半导体材料在光照下的降解过程

No abstract available

Solar energy represents a robust and natural form of resource for environment remediation via photocatalytic pollutant degradation with minimum associated costs. However, due to the complexity of the photodegradation process, it has been a long-standing challenge to develop reliable photocatalytic systems with low recombination rates, excellent recyclability, and high utilization rates of solar energy, especially in the visible light range. In this work, a ternary hetero-nanostructured Ag-CuO-ZnO nanotube (NT) composite is fabricated via facile and low-temperature chemical and photochemical deposition methods. Under visible light irradiation, the as-synthesized ZnO NT based ternary composite exhibits a greater enhancement (∼300%) of photocatalytic activity than its counterpart, Ag-CuO-ZnO nanorods (NRs), in pollutant degradation. The enhanced photocatalytic capability is primarily attributed to the intensified visible light harvesting, efficient charge carrier separation and much larger surface area. Furthermore, our as-synthesised hybrid ternary Ag-CuO-ZnO NT composite demonstrates much higher photostability and retains ∼98% of degradation efficiency even after 20 usage cycles, which can be mainly ascribed to the more stable polar planes of ZnO NTs than those of ZnO NRs. These results afford a new route to construct ternary heterostructured composites with perdurable performance in sewage treatment and photocorrosion suppression.

Halide perovskites (HaP), with their exceptional optoelectronic properties and high‐power conversion efficiencies in photovoltaic devices, hold promise for photoelectrochemical (PEC) applications in green fuel and chemical production. However, their stability in aqueous environments remains a challenge. This study investigates the stability and degradation mechanisms of the 2D Ruddlesden‐Popper phase phenylethyl ammonium lead iodide (PEA(+)2PbI4) thin films in aqueous electrolytes under dark and illuminated conditions. While PEA(+)2PbI4 thin films appear to be thermodynamically stable in an aqueous electrolyte with phenylethyl ammonium iodide (PEAI), illumination causes significant photodegradation generating a deprotonated and dehalogenated 2D intercalation product: phenylethylamine‐lead iodide, 2PEA(0)‐PbI2. The degradation of the 2D semiconductor leads to substantial reduction in the photovoltage, adversely impacting the material performance in photoelectrochemical (PEC) devices. To intercept photo‐excited charge carriers in the 2D semiconductor, the I3−/I− redox is added, which reduced photodegradation. The findings underscore that while catalytic reactions at halide perovskite electrodes in aqueous electrolytes are feasible, reversible and irreversible photodegradation remains a critical limitation that must be addressed in the design of PEC devices employing metal halide semiconductor layers for direct electrochemical energy conversion.

Photocatalysis is an effective solution for wastewater treatment problems, and semiconductor heterojunctions for photocatalysis can effectively separate photogenerated carriers to improve the photocatalytic degradation efficiency of pollutants. In this study, a heterojunction photocatalyst with a ZnO/Zn2SnO4 composite structure was fabricated to degrade methylene blue (MB) and rhodamine B (RhB) dyes using visible light. The crystal structure, size, chemical composition, valence state, vibrational modes, and chemical composition of the ZnO/Zn2SnO4 photocatalyst were analyzed by XRD, TEM, EDX, XPS, and Raman spectroscopy. The absorption properties, band gap, and photoluminescence properties investigated by UV–Vis absorption and photoluminescence spectra. In addition, the photodegradation mechanism and charge transfer of the ZnO/Zn2SnO4 heterostructure were analyzed in detail. The ZnO/Zn2SnO4 composites showed the characteristic peaks of ZnO and Zn2SnO4, proving the formation of their heterostructure. In the photodegradation experiment under visible light, the ZS80 sample exhibited the best photocatalytic degradation performance of 93.11% for MB and 97.13% for RhB after 120 min of lighting. In addition, the ZnO/Zn2SnO4 composites showed an increase in the lifetime of the photogenerated charged carriers and a decrease in the recombination of photogenerated electron–hole pairs. Its heterostructure effectively inhibited electron–hole recombination, remarkably improved the activity and stability of the catalyst, and promoted the catalytic reaction efficiency. The superior photodegradation performance of the heterostructure makes it applicable in the degradation of environmental pollutants.

Although many efforts to study photodegradation of organic semiconductor (OSC) thin films have been reported, few consider the effect of substrate material on degradation pathways. Given the many electrode contacts...

Bentonite-supported TiO2 (Montmorillonite (MMT)-TiO2) and Cu3TiO5 oxides (MMT-Cu3TiO5) nanomaterials were synthesized via a facile and sustainable sol–gel synthesis approach. The XRD results indicate the presence of mixed phases, namely, TiO2 anatase and a new semiconductor, Cu3TiO5, in the material. The specific surface area (SBET) exhibits a notable increase with the incorporation of TiO2 and Cu3TiO5, rising from 85 m2/g for pure montmorillonite to 245 m2/g for MMT-TiO2 and 279 m2/g for MMT-Cu3TiO5. The lower gap energy of MMT-Cu3TiO5 (2.15 eV) in comparison to MMT-TiO2 (2.7 eV) indicates that MMT-Cu3TiO5 is capable of more efficient absorption of visible light with longer wavelengths. The immobilization of TiO2 and Cu3TiO5 on bentonite not only enhances the textural properties of the samples but also augments their visible light absorption capabilities, rendering them potentially more efficacious for adsorption and photocatalytic applications. The photocatalytic efficacy of both MMT-TiO2 and MMT-Cu3TiO5 was evaluated through the monitoring of the degradation of Orange G, an anionic azo dye. The MMT-Cu3TiO5 photocatalyst was observed to induce complete degradation (100%) of the Orange G dye in 120 min when tested in an optimized reaction medium with a pH of 3 and a catalyst concentration of 2 g/L. MMT-Cu3TiO5 was demonstrated to be an exceptionally effective catalyst for the degradation of Orange G. Following the synthesis of the catalyst, it can be simply washed with the same recovered solution and reused multiple times for the photocatalytic process without the need for any chemical additives.

The extensive application of 2,4-dichlorophenoxyacetic acid (2,4-D, C8H6Cl2O3) as a herbicide has resulted in the significant environmental contamination. This pervasive pollution poses serious health risks to humans. Semiconductor photocatalytic technology represents a highly effective approach to addressing urgent environmental crisis. Herein, thin-layer g-C3N4 nanosheets were synthesized using NH4Cl as a dynamic gas template. Among all synthesized materials, the thin-layer g-C3N4 (2.5N-MCN) exhibited a degradation rate constant (k) for 2,4-D that was 3.05 times higher than that of pristine g-C3N4 (MCN). 2.5N-MCN exhibits continuous lamellar nanostructures, the highest specific surface area (SBET), and superior electrochemical properties among all samples. Moreover, the hydroxyl radical (·OH) was identified as the predominant reactive species in the photocatalytic degradation process. Subsequently, the degradation pathway of 2,4-D was deduced from the identified intermediates. And the process of photocatalytic degradation 2,4-D proceeded without significant elevated in toxicity levels by the TEST software. Then, the pH and fulvic acid influence experiment were also studied. Nevertheless, the photocatalytic degradation efficiency of 2.5N-MCN toward 2,4-D exhibited a moderate decline after four cycles. This research provided insights into the improving the photocatalytic efficiency of organic pollutant degradation through efficient solar conversion materials.

In this paper, by employing an eco-friendly and green approach, semiconductor CuO/ZnO nanocomposite are synthesized using an aqueous extract of Urtica urens. FT-IR, XRD, TEM, SAED, EDX, TGA, and UV-Vis spectroscopy were used for semiconductor characterization. The data revealed the successful formation of crystalline spherical nanocomposites with sizes ranging from 5 to 45 nm. The main components of the synthesized nanocomposites were Cu, Zn, and O, which had different weights and atomic percentages. The maximum absorbance of nanocomposites was 358 nm, with a direct bandgap of 2.25 eV, which is suitable for photocatalysis under visible light. The maximum photocatalytic activity of the synthesized semiconductor nanocomposites for photodegradation of methylene blue dye was 95.8%, where it was 44.5% and 65.5% for monometallic CuO and ZnO, respectively. The optimum conditions for maximum photocatalytic activity were a pH of 9, a dye concentration of 5 mg L−1, and nanocomposite concentration of 1.0 mg mL−1 after 70 min. The reusability of the synthesized semiconductor was promising for the fourth cycle, with a reduced capacity of 5%. Complementary investigations, antimicrobial activity and cytotoxic activity, were performed to increase the application of semiconductor nanocomposites. The data revealed the promising activity of the nanocomposite against E. coli, P. aeruginosa, B. subtilis, S. aureus, C. parapsilosis, C. albicans, and C. tropicalis with low MICs ranging between 50 and 25 µg mL−1. Additionally, compared with normal cell line, the synthesized nanocomposite targeted the cancer cell line HepG2 with a low IC50 value of 69.9 µg mL−1 (vs. IC50 220 µg mL−1 of normal cell line HFB4). Overall, the green-synthesized semiconductor CuO/ZnO nanocomposite showed promising activity as environmental contaminant cleaner and was integrated with antimicrobial and in vitro cytotoxic activities.

No abstract available

In this study, nanostructured ferberites (FeWO4) were synthesized via hydrothermal routes in an acidic medium. It was then investigated as an efficient photocatalyst for degrading organic dye molecules, with methylene blue (MB) as a model pollutant. The formation mechanism of ferberite revealed that the physical form of the precursor, FeSO4·7H2O, acts as a decisive factor in morphological evolution. Depending on whether it is in a solid or dilute solution form, two distinct nanostructures are produced: nanoplatelets and self-organized microspheres. Both structures are composed of stoichiometric FeWO4 (Fe: 49%, W: 51%) in a single monoclinic phase (space group P2/c:1) with high purity and crystallinity. The p-type semiconductor behavior was confirmed using Mott–Schottky model and the optical analysis, resulting in small band gap energies (≈1.7 eV) favoring visible absorption light. Photocatalytic tests under simulated solar irradiation revealed rapid and efficient degradation in less than 10 min under near-industrial conditions (pH 5). This was achieved using only a ferberite catalyst and a low concentration of H2O2 (4 mM) without additives, dopants, or artificial light sources. Advanced studies based on photocurrent measurements, trapping and stability tests were carried out to identify the main reactive species involved in the photocatalytic process and better understanding of photodegradation mechanisms. These results demonstrate the potential of nanostructured FeWO4 as a sustainable and effective photocatalyst for water purification applications.

Organic semiconductor photocatalysts typically suffer from high exciton binding energies (Eb) due to their low dielectric constants, which limit further improvement in photocatalytic efficiency. However, current strategies that rely on polar groups or ion doping struggle to balance high dielectric gain and long-term stability due to dipole disorder and complex synthesis. Herein, dipole polarization modulation is reported by breaking geometric symmetry in conjugated porous polymers (CPPs) to enhance the dielectric constant and achieve a low Eb of 57.6 meV. The low Eb enhances the separation and transport efficiency of photogenerated charge carriers. As a demonstration, these CPPs are subjected to photocatalytic antibiotic degradation, achieving an ofloxacin removal efficiency of 99.1% under ambient conditions. The results provide new insights into the rational design of porous materials with low Eb for efficient photocatalysis.

MXenes (Ti3C2) have gained significant research attention in the domain of photocatalysis due to their well-defined planar structure, exceptional metallic conductivity, diverse elemental content, terminations of surface groups and numerous derivatives. The utilization of MXene-derived and based materials serves as a compelling rationale for developing creative photocatalysts that exhibit both optimal activity and long-term stability. Titanium dioxide (TiO2) has emerged as the most thoroughly researched photocatalyst due to its exceptional photocatalytic activity, affordability, lack of toxicity and abundant availability. However, TiO2-based technologies are characterized by significant limitations, including a broadband gap and the rapid recombination of photoinduced charge carriers. Extensive research explores MXene's role in enhancing TiO2 through MXene/TiO2 nanocomposite synthesis. These nanocomposites enable efficient electron transport at the metal-semiconductor interface, with MXene serving as a co-catalyst or support to enhance catalytic activity. Traditional membrane separation techniques pose challenges, when efficiently removing contaminants as a result of fouling and pressure-related concerns. To address these constraints, novel membrane technologies, including photocatalytic membranes have been developed. By implementing these hybrid techniques the overdependence on size exclusion mechanisms can be bypassed, thereby enabling more effective separation of pollutants. This study addresses the recent advances in MXene/TiO2-based photocatalytic membrane technology to eliminate new contaminants and improve pollutant removal when utilized with existing treatment methods.

No abstract available

Generally, semiconductor photocatalyst can only absorbed ultraviolet light and easily reunited in the using process, which affected their catalytic efficiency. In this work, the calcium alginate/polypyrrole/titanium dioxide (CA/PPy/TiO2) aerogel was prepared to photodegrade Congo red (CR) dye. The sensitization of TiO2 with PPy enabled energy absorption in visible light. The X-ray photoelectron spectrum (XPS) result confirmed hydrogen bonds between PPy and TiO2 proving tight combination between them. Ultraviolet-visible diffuse reflectance spectrum verified optical band gap narrowing of PPy/TiO2 in contrast to TiO2. When CA aerogel loaded with 0.6 g PPy/TiO2 nanoparticles, catalytic activity was the highest. The total degradation rate reached 81.1 % for a 30 mg/L CR solution at pH = 3. The degradation rate of CA/PPy/TiO2 was more than twice that of CA/TiO2. CA/PPy/TiO2 aerogel can immerse in water for a long time and keep structural integrity due to good swelling resistance, which surpassed most bio-based aerogels. This aerogel can effectively remove organic contaminants using just visible light and had high stability under strong acid and alkali conditions, which was appropriate for most water pollution control. This method of combining aerogel with photocatalyst might open up a new window for wastewater treatment.

No abstract available

No abstract available

A high-throughput sonochemical synthesis and testing strategy was developed to discover covalent organic frameworks (COFs) for photocatalysis. In total, 76 conjugated polymers were synthesized, including 60 crystalline COFs of which 18 were previously unreported. These COFs were then screened for photocatalytic hydrogen peroxide (H2O2) production using water and oxygen. One of these COFs, sonoCOF-F2, was found to be an excellent photocatalyst for photocatalytic H2O2 production even in the absence of sacrificial donors. However, after long-term photocatalytic tests (96 h), the imine sonoCOF-F2 transformed into an amide-linked COF with reduced crystallinity and loss of electronic conjugation, decreasing the photocatalytic activity. When benzyl alcohol was introduced to form a two-phase catalytic system, the photostability of sonoCOF-F2 was greatly enhanced, leading to stable H2O2 production for at least 1 week.

The development of high-efficiency organic solar cells (OSCs) processed from non-halogenated solvents is crucially important for their scale-up industry production. However, owing to the difficulty of regulating molecular aggregation, there is a huge efficiency gap between non-halogenated and halogenated solvent processed OSCs. Herein, we fabricate o-xylene processed OSCs with approaching 20% efficiency by incorporating of a trimeric guest acceptor named Tri-V into the PM6:L8-BO-X host blend. The incorporation of Tri-V effectively restricts the excessive aggregation of L8-BO-X, and optimizes the phase-separation morphology, which leads to mitigated trap density states, reduced energy loss and suppressed charge recombination. Consequently, the PM6:L8-BO-X:Tri-V-based device achieves an efficiency of 19.82%, representing the highest efficiency for green-solvent processed OSCs reported to date. Noticeably, with the addition of Tri-V, the ternary device shows an improved photostability than binary PM6:L8-BO-X-based device, and maintains 80% of the initial efficiency after continuous illumination for 1380 h. This work provides a feasible approach for fabricating high-efficiency, stable, eco-friendly OSCs, and sheds new light on the large-scale industrial production of OSCs.

No abstract available

Summary 2D lead halide perovskites are used to improve device operational stability due to increased environmental stability and reduced ion migration compared to 3D perovskites. However, the relationship between the 2D perovskite stability under illumination and spacer cation is still not well understood. Thus, we examine photoinduced halide segregation (PHS) in different 2D mixed-halide perovskites and show that PHS is suppressed in the materials which have photostable bromide halide phase. As the spacer cations provide the barrier to ion migration in 2D perovskites, PHS would be facilitated by the loss of spacer cations through their interactions with various mobile oxidized halide species, resulting in organic ammonium deprotonation and spacer cation vacancy formation. The existence of a photostable A2PbBr4 phase, which does not exhibit spacer cation loss, results in the suppression of PHS in 2D mixed halide perovskites due to reduced spacer vacancy formation and consequently reduced halide ion migration under illumination.

In this present work, the preparation of ternary MoS2–NiO–CuO nanohybrid by a facile hydrothermal process for photocatalytic and photovoltaic performance is presented. The prepared nanomaterials were confirmed by physio-chemical characterization. The nanosphere morphology was confirmed by electron microscopy techniques for the MoS2–NiO–CuO nanohybrid. The MoS2–NiO–CuO nanohybrid demonstrated enhanced crystal violet (CV) dye photodegradation which increased from 50 to 95% at 80 min; The degradation of methyl orange (MO) dye increased from 56 to 93% at 100 min under UV–visible light irradiation. The trapping experiment was carried out using different solvents for active species and the Z-Scheme photocatalytic mechanism was discussed in detail. Additionally, a batch series of stability experiments were carried out to determine the photostability of materials, and the results suggest that the MoS2–NiO–CuO nanohybrid is more stable even after four continuous cycles of photocatalytic activity. The MoS2–NiO–CuO nanohybrid delivers photoconversion efficiency (4.92%) explored efficacy is 3.8 times higher than the bare MoS2 (1.27%). The overall results indicated that the MoS2–NiO–CuO nanohybrid nanostructure could be a potential candidate to be used to improve photocatalytic performance and DSSC solar cell applications as well.

In this study, a novel flowerball-like CdS/O-g-C3N4 heterostructure was successfully synthesized using an in-situ solvothermal method and evaluated for its photocatalytic performance in methylene blue (MB) degradation, hydrogen (H2) evolution, and photostability. Owing to its gradient band alignment, the heterostructure exhibits enhanced visible-light absorption and efficient separation of photogenerated charge carriers. Among the prepared structures, the optimized CdS/OCN-10 m demonstrated superior photocatalytic efficiency, completely degrading 10 mg/L of MB within 120 min under visible light. The apparent rate constant for MB degradation by CdS/OCN-10 m was calculated as 0.0123 min-1, which is approximately 2.5 times and 2.1 times higher than those of O-g-C3N4 (0.00479 min-1) and CdS (0.0057 min-1), respectively. Moreover, CdS/OCN-10 m exhibited an outstanding hydrogen evolution rate of 48,000 μmol/g, outperforming pure CdS and O-g-C3N4 by factors of 5.8 and 3.2, respectively. These enhanced properties were further confirmed through various characterization techniques, including photoluminescence (PL) spectroscopy, UV-vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), and transient photocurrent response measurements. Importantly, the CdS/OCN-10 m photocatalyst showed excellent stability, retaining its flowerball-like morphology and exhibiting negligible performance loss over five photocatalytic cycles spanning 25 h, underscoring its strong resistance to photocorrosion.

An efficient and straightforward synthetic strategy has been established for the synthesis of biologically relevant thiophosphates. This method relies on visible light-induced oxidative dehydrogenative coupling between thiols and P(O)H compounds, utilizing lead-free Cs3Bi2Br9 perovskite as a heterogeneous photocatalyst with air serving as the oxidant. The reaction proceeds efficiently in 2-methyl tetrahydrofuran (2-MeTHF) under ambient temperature conditions, exhibits good tolerance towards a wide range of functional groups, and affords the target products in high yields. Furthermore, the photocatalyst can be readily recycled for at least 5 runs in gram-scale synthesis without a significant loss of catalytic activity.

A porous organic polymer (POP) based on hexakis(4-formylphenoxy)cyclophosphazene (HFCP), that is, HFCPTzPOP, was synthesized by condensation reaction with dithiooxamide. The polymer is shown to exhibit excellent visible light absorption, enabling its application as a heterogeneous photocatalyst for the conversion of indoles to isatins and 3-thiocyanoindoles, and selective thiocyanation of anilines at the para position. The photocatalytic reactions occur under mild conditions in oxygen atmosphere without the addition of any toxic metal or oxidizing agent. HFCPTzPOP acts as a photoredox catalyst in oxidative transformations, converting molecular oxygen into singlet oxygen (1O2) and superoxide radical anion (O2 •-) through energy transfer and electron transfer processes, respectively. It is shown that the photocatalyst can be easily recycled up to 10 cycles without any loss of catalytic activity.

Organic photovoltaics (OPVs) show great promise for both outdoor and indoor applications. However, there remains a lack of understanding around the stability of OPVs, particularly for indoor applications. In this work, the photostability of the poly[(thiophene)‐alt‐(6,7‐difluoro‐2‐(2‐hexyldecyloxy)quinoxaline)]:2,2′‐((2Z,2′Z)‐((4,4,9,9‐tetrahexyl‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile blend is investigated for both outdoor and indoor applications. Photostability is found to vary drastically with illumination intensity. Devices under high‐intensity white light‐emitting diode (LED) illumination, with their short‐circuit current density (JSC) matching JSC–EQE for AM1.5 G illumination, lose 42% of their initial performance after 30 days of illumination. Contrastingly, after almost 47 days of illumination devices under 1000 lux white LED illumination show no loss in performance. The poor photostability under 1 sun illumination is linked to the poor photostability of IDIC. Through Raman spectroscopy and mass spectrometry, IDIC is found to suffer from photoisomerization, which detrimentally impacts light absorption and carrier extraction. In this work, it is highlighted that under low light levels, the requirement of intrinsic material photostability may be less stringent.

Till date it is a great challenge to synthesize CdS photocatalyst with a high stability. In this study, a stable CdS photocatalyst was successfully synthesized by a simple, cost‐effective hydrothermal route via cadmium acetate and thiourea as Cd and S precursors, respectively. The effect of different processing times (8 h and 24 h) and molar ratios on the photocatalytic activity and stability were mainly investigated. The samples were characterized in detail by XRD, FT‐IR, XPS, UV‐vis DRS, Photolummiscence spectroscopy and Surface photovoltage. The photocatalytic activity of the as‐obtained nanostructures was examined for methylene blue (MB) dye degradation under visible light irradiation (λ≥420 nm). After 70 min of irradiation, nearly 82 % of MB was degraded by CdS nanostructures, display an improved photocatalytic activity for MB degradation with an apparent rate constant (k) of 0.019 min−1. Additionally, CdS nanostructures sustained a good photostability after five consecutive cycles. The higher photocatalytic activity of CdS nanostructure is attributed to an efficient separation of photogenerated electron‐hole pairs stimulated by its optimal molar ratio, optimal temperature and surface morphology. Our synthesized stable nanostructures have potential for dye contaminated waste‐water treatment.

No abstract available

Abstract Carbon nitride photocatalysts are among the most studied candidates for efficient solar hydrogen (H2) production due to their abundance of precursors, suitable bandgap, and visible light utilization. However, the polymeric nature of carbon nitride materials raises concerns regarding the self‐decomposition during photocatalytic redox processes. Yet, the operational stability of carbon nitride photocatalysts for solar H2 production remains under‐explored. Here we evaluate the photostability of carbon nitride photocatalysts with platinum (Pt) as the co‐catalyst for solar H2 evolution and significant deactivation of this photocatalyst is observed under'accelerated’ testing conditions. It is demonstrated that the detachment of the Pt co‐catalyst on the surface of carbon nitride is the major reason for this deactivation, which can be attributed to a synergistic effect of photo‐corrosion and mechanical stirring. The photo‐corrosion weakens the interfacial bonding between carbon nitride and Pt co‐catalyst, while continuous collisions from the mechanical stirring promote the detachment of co‐catalysts from the surface of carbon nitride. These understandings provide insights into the rational design of photocatalysts and photocatalytic systems for improved operational stability.

Titanium dioxide TiO2/gellan gum (GG) in different compositions (1, 3, and 5% GG) was investigated to degrade methylene blue (MB) under UV light. XRD, SEM, and EDS confirmed the anatase phase. The textural properties demonstrated the formation of mesopores. The band gaps were 3.2 eV, 3.0 eV, and 2.9 eV. A photodegradation of MB of 95% was observed using the lowest gum concentration. It was attributed to the photogenerated radicals and the specific surface area. The FTIR spectra showed the photostability of the catalyst after successive cycles. The toxicity tests demonstrated no toxicity after dye degradation. Therefore, TiO2/GG is promising for the treatment of water.

In the present study, Ba-doped Ag3PO4/SnO2 type-II heterojunction nanocomposites were fabricated and systemically investigated for the degradation of basic yellow 28 (BY28) dye and Cr(VI) reduction in the photocatalytic process under visible-light irradiation. XRD, XPS, FESEM, DRS, and PL analyses were performed to determine the characterization of synthesized photocatalysts. The optimal 1.5 wt% Ba-doped Ag3PO4/SnO2 nanocomposite exhibited an efficient photocatalytic activity with rate constant of 0.0491 min−1 for BY28 degradation and 0.0261 min−1 for Cr(VI) reduction, which is 13.3 and 7.5 times higher than that of the SnO2 nanorods. Such enhanced performance can arise from the one-dimensional structure, extended light absorption toward the visible region, formation of the type II heterojunction, the new defect-related energy states, and efficient charge separation. Furthermore, the photostability of the photocatalysts was studied and a plausible photocatalytic mechanism was proposed.

Covalent organic frameworks (COFs) serve as an excellent foundation for heterogeneous photocatalysis. Herein, we synthesized an anthraquinone‐based COF (TpAQ) on a gram scale via a mechanochemical grinding pathway. This COF was employed as a visible‐light‐harvesting photocatalyst for selective fluorination of benzylic C─H bonds and perfluoroalkylation of arenes. The carbonyl core in the anthraquinone linker facilitated benzylic fluorination through a hydrogen atom transfer (HAT) pathway. Control experiments and photophysical analysis were conducted to gain deeper insight into the reaction mechanism. The recyclability up to the fifth cycle without significant loss of yield (>90%) highlighted the robustness of the catalyst. This reaction strategy was also executed on a gram scale to validate the scalability of the protocol.

Carbon dots are a novel carbon-based material with the appealing properties of inexpensive nanomaterials, low toxicity, environmental tolerance, abundance, photostability, and simplicity of synthesis. Carbon dots (CDs) have effectively distinguished themselves from other materials due to their superior properties, such as ultra-small size, good photostability, excellent biocompatibility, and tunable fluorescence properties. This study synthesized carbon dots from green algae using a hydrothermal method at 180 °C and doped with nitrogen. Green algae contain carbohydrates, proteins, and poly-unsaturated fatty acids, allowing them to produce more carbon and be used as a precursor in synthesizing carbon dots. The FT-IR and UV-Vis spectra reveal the distinct functionalization and energy gap between the surface states of CDs and N-CDs. The carbon nanoparticles were then used as photocatalysts to degrade methyl red. The results indicate that nitrogen doping is superior for reducing methyl red and has tremendous potential for environmental applications.

Solar-driven flat-panel H2O-to-H2 conversion is an important technology for value-added solar fuel production. However, most frequently used particulate photocatalysts are hard to achieve stable photocatalysis in flat-panel reaction module due to the influence of mechanical shear force. Herein, a highly active CdS@SiO2-Pt composite with rapid CdS-to-Pt electron transfer and restrained photoexciton recombination was prepared to process into an organic-inorganic membrane by compounding with polyvinylidene fluoride (PVDF). This PVDF networked organic-inorganic membrane displays high photostability and excellent operability, achieving improved simulated sunlight-driven alkaline H2O-to-H2 conversion activity (213.48 mmol m−2 h−1) following a 0.68% of solar-to-hydrogen efficiency. No obvious variation in its appearance and micromorphology was observed even being recycled for 50-times, which considerably outperforms the existing membrane photocatalysts. Subsequently, a homemade panel H2O-to-H2 conversion system was fabricated to obtain a 0.05% of solar-to-hydrogen efficiency. In this study, we opens up a prospect for practical application of photocatalysis technology. Solar-driven flat-panel H2O-to-H2 conversion is an important technology for value-added solar fuel production. Here, an organic-inorganic interface membrane catalyst displays high photostability and operability with 0.68% solar-to-hydrogen efficiency.

A good photocatalyst maximizes the absorption of excitation light while reducing the recombination of photogenerated carriers. Among visible light responsive materials, CdS has good carrier transport capacity; however, its photostability is poor and limits its use. Here, the synthesis of a new hydrothermal CdS is reported, and post-synthesis annealing determines crystal properties and spectroscopic characteristics. The introduction of sulfur vacancies as intra band gap states is the key factor for the enhancement of photocatalytic activity. In fact, by spectroscopic and photo-electrochemical experiments, we demonstrate that sulfur vacancies act as an electron sink, favoring the charge transfer process to methyl orange. In addition, the studied hydrothermal CdS is characterized by very high stability, thus enabling a visible-light active photocatalyst that is overall recyclable, stable and more efficient than the commercial benchmark.

Although the development of radical chain and photocatalytic borylation reactions using N-heterocyclic carbene (NHC)-borane as boron source is remarkable, the persistent problems, including the use of hazardous and high-energy radical initiators or the recyclability and photostability issues of soluble homogeneous photocatalysts, still leave great room for further development in a sustainable manner. Herein, we report a conceptually different approach toward highly functionalized organoborane synthesis by using recoverable ultrathin cadmium sulfide (CdS) nanosheets as a heterogeneous photocatalyst, and a general and mild borylation platform that enables regioselective borylation of a wide variety of alkenes (arylethenes, trifluoromethylalkenes, α,β-unsaturated carbonyl compounds and nitriles), alkynes, imines and electron-poor aromatic rings with NHC-borane as boryl radical precursor. Mechanistic studies and density functional theory (DFT) calculations reveal that both photogenerated electrons and holes on the CdS fully perform their own roles, thereby resulting in enhancement of photocatalytic activity and stability of CdS.

In this article, we present the synthesis of calcium sulfate nanoparticles (CaSO4 NPs) from waste chalk powder by the calcination method. These CaSO4 NPs were utilized for the construction of a mesoporous graphitic carbon nitride-calcium sulfate (mpg-C3N4-CaSO4) photocatalyst. Synthesized materials were confirmed by several characterization techniques. The photocatalytic performance of the synthesized samples was tested by the degradation of methylene blue (MB) in the presence of both UV-vis light and sunlight. The efficiency of photocatalytic degradation of MB dye using the optimized mpg-C3N4-CaSO4-2 composite reached 91% within 90 min in the presence of UV-vis light with superb photostability and recyclability after five runs compared to individual mpg-C3N4 and CaSO4 NPs and reached 95% within 120 min under sunlight. Histotoxicological studies on fish liver and ovary indicated that the dye containing the solution damaged the structure of the liver and ovary tissues, whereas the photodegraded solution of MB was found to be less toxic and caused negligible alterations in their typical structure similar to the control group.

Although organic solar cells (OSCs) have received increasing attention because of their high device efficiencies, the fundamental mechanism governing their photostability remains elusive. Herein, the effect of the luminescence stability of the acceptor components on the burn‐in voltage loss of binary and ternary OSCs is demonstrated. A systematic characterization reveals that the acceptor component experiences an abnormal decrease in luminescence under photoaging—specifically, photoinduced luminescence quenching—because of a photoinduced conformational change. This phenomenon increases nonradiative recombination in blends and thus causes a substantial nonradiative voltage loss of OSCs. Moreover, an introduction of a third component with high luminescence stability can effectively reduce the burn‐in voltage loss of OSCs. A composition‐dependent photostability study of the resultant ternary OSCs reveals that the reduction in the burn‐in voltage loss of OSCs is mainly driven by the third component distributed in the mixed phase; high luminescence stability of this component effectively prevents the increase in nonradiative voltage loss by photoaging. The results suggest that improving the luminescence stability of the acceptor components can be an effective method for highly stable photovoltaics with greatly reduced burn‐in voltage loss.

The paper critically addresses two contemporary environmental challenges, the water crisis and the unrestricted discharge of organic pollutants in waterways together. An eco-friendly method was used to fabricate a cellulose/g-C3N4/TiO2 photocatalytic composite that displayed a remarkable degradation of methylene blue dye and atenolol drug under natural sunlight. Introducing graphitic carbon nitride (g-C3N4) onto pristine TiO2 improved hybrid material’s photonic efficacy and enhanced interfacial charge separation. Furthermore, immobilizing TiO2/g-C3N4 on a semi-interpenetrating cellulose matrix promoted photocatalyst recovery and its reuse, ensuring practical affordability. Under optimized conditions, the nano-photocatalyst exhibited ∼95% degradation of both contaminants within two hours while retaining ∼55% activity after ten cycles demonstrating a promising photostability. The nano-photocatalyst caused 66% and 57% reduction in COD and TOC values in industrial wastewater containing these pollutants. The photocatalysis was fitted to various models to elucidate the degradation kinetics, while LC-MS results suggested the mineralization pathway of dye majorly via ring opening demethylation. >98% disinfection was achieved against E. coli (104–105 CFU·ml−1) contaminated water. This study thus paves multifaceted strategies to treat wastewater contaminants at environmental levels employing nano-photocatalysis.

No abstract available

No abstract available

Herein we present a combined study of the evolution of both the photoluminescence (PL) and the surface chemical structure of organic metal halide perovskites as the environmental oxygen pressure rises from ultrahigh vacuum up to a few thousandths of an atmosphere. Analyzing the changes occurring at the semiconductor surface upon photoexcitation under a controlled oxygen atmosphere in an X-ray photoelectron spectroscopy (XPS) chamber, we can rationalize the rich variety of photophysical phenomena observed and provide a plausible explanation for light-induced ion migration, one of the most conspicuous and debated concomitant effects detected during photoexcitation. We find direct evidence of the formation of a superficial layer of negatively charged oxygen species capable of repelling the halide anions away from the surface and toward the bulk. The reported PL transient dynamics, the partial recovery of the initial state when photoexcitation stops, and the eventual degradation after intense exposure times can thus be rationalized.

Through regulating the pH values, a series of iodo-argentate/cuprate hybrids, [Me3 (4-TPT)]4 [Ag6 I18 ] (1, Me3 (4-TPT)=N,N',N''-trimethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine), [Me3 (4-TPT)][M5 I8 ] (M=Ag/2, Cu/2 a), [Me3 (3-TPT)][M5 I8 ] (Me3 (3-TPT)=N,N',N''-trimethyl-2,4,6-tris(3-pyridyl)-1,3,5-triazine, M=Ag/3, Cu/4), which exhibit adjustable structural variations with different dimensional structures, have been obtained under solvothermal conditions. They are directed by two types of in situ N-alkylation TPT-derivatives (Me3 (4-TPT) for 1/2/2 a and Me3 (3-TPT) for 3/4) and represent the isolated units (1), 1D polymeric chain (4), 2D layered structures (2/2 a, 3) based on diverse metal iodide clusters. These compounds possess reducing band gaps as compared with the bulk β-AgI and CuI and belong to potential semiconductor materials. Iodocuprates feature highly efficient photocatalytic activity in the sunlight-induced degradation of organic dyes. The detailed study on the possible photocatalytic mechanism, including radical trapping tests and theoretical calculations, reveals that the N-alkylation TPT moieties contribute to the narrow semiconducting behavior and effectively inhibit the recombination of photogenerated electron-hole pairs, which result in an excellent visible-light-induced photocatalytic performance.

Photocatalytic oxidation technology harnesses solar energy for pollutant mineralization, presenting significant potential for environmental applications. A critical bottleneck remains the development of high-performance photocatalysts. This study centers on the non-metallic semiconductor material graphitic carbon nitride (g-C3N4). To overcome the inherent limitations of pristine g-C3N4, including limited surface area, rapid charge carrier recombination, and inadequate active sites, it implements surface engineering strategies employing acidic (H2SO4) or basic (K2CO3) agents to modulate microstructure, introduce defect sites (cyano/amino groups), and optimize bandgap engineering. These modifications synergistically enhanced photogenerated charge carrier separation efficiency and surface reactivity, leading to efficient dye degradation. Notably, the K2CO3-modified catalyst (g-C3N4-OH), synthesized with a mass ratio of m(g-C3N4):m(K2CO3) = 1:1, achieved 92.2% Rhodamine B degradation within 50 min under visible light, surpassing pristine g-C3N4 (20.6%), the optimized H2SO4-modified sample (g-C3N4-HS, 60.9%), and even template-synthesized g-C3N4-SBA (79.6%). The g-C3N4-OH catalyst demonstrated exceptional performance under both visible light and natural solar illumination. Combining facile synthesis, cost-effectiveness, superior activity, and robust stability, this work provides a novel approach for developing high-efficiency non-metallic photocatalysts applicable to dye wastewater.

Employing in situ N-alkylation of the conjugated compound 9,10-bis(4-pyridyl)anthracene (bpanth) as structure-directing agent, a 3D inorganic-organic hybrid iodoplumbate, [Me2 (bpanth)][Pb4 I10 ] (1), was solvothermally prepared. The in situ N-alkylation of bpanth with alcohols was investigated. 1 features a novel 3D open framework based on an interesting Pb6 I24 cluster. UV/Vis spectroscopy analyses indicate that 1 is a potential semiconductor material with a narrow energy gap of 2.06 eV. It exhibits good catalytic activity in the visible-light-drived degradation of an organic dye. This work further illustrates that introducing conjugated organic molecules as templates is conducive to achieving semiconducting hybrid halometallates with narrow band gaps.

In this work, the solar light-induced redox photoactivity of ZnO semiconductor material was used to prepare CuxO-ZnO composite catalysts at room temperature with a control of the chemical state of the copper oxide phase. Cu2(I)O-ZnO and Cu(II)O-ZnO composite catalysts were prepared by using Cu(acac)2 in tetrahydrofuran-water and Cu(NO3)2 in water as metallic precursor, respectively. Prior to the implementation of the photon-assisted synthesis method, the most efficient photoactive ZnO material was selected from among different ZnO materials prepared by the low temperature polyol and precipitation methods with carbonates and carbamates as precipitation agents. The photocatalytic degradation of the 4-chlorophenol compound in water under simulated solar light was taken as a model reaction. The ZnO support materials were characterized by X-ray diffraction (XRD), surface area and porosimetry measurements, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the synthesis method strongly influenced their photoactivity in terms of 4-chlorophenol degradation and of total organic carbon removal. The most photoactive ZnO material was prepared by precipitation with carbonates and calcined at 300 °C, benefitting from a high specific surface area and a small mean crystallite size for achieving a complete 4-chlorophenol mineralization within 70 min of reaction, with minimum Zn2+ released to the solution. Besides thermal catalysis applications, this work has opened a new route for the facile synthesis of Cu2O-ZnO heterojunction photocatalysts that could take place under solar light of the heterojunction built between the p-type semi-conductor Cu2O with direct visible light band gap and the ZnO semiconductor phase.

Utilization of a solar-driven semiconductor as a photocatalyst to degrade antibiotic pollutants is a feasible and environmentally friendly technology. In this paper, 3D chrysanthemum-like g-C3N4/TiO2 as a visible-light-driven hybrid photocatalyst with a Z-scheme heterostructure was firstly synthesized by the in situ hydrothermal synthesis method. Experiments proved that this 3D chrysanthemum-like g-C3N4/TiO2 had better degradation performance toward tetracycline than TiO2 and g-C3N4. In particular, when optimized g-C3N4/TiO2-2 was applied for tetracycline removal (200 ml, 10 mg L-1), the corresponding degradation efficiency could reach nearly 100% within 60 min. The improved photocatalytic activity was the result of better utilization of the heterostructure-induced visible light, more efficient charge transfer in the Z-scheme heterojunction as well as stronger redox capability. The Z-scheme degradation mechanism was supported by the trapping experiments of active species and ESR radical detection, and the whole photocatalytic process was controlled by the combined action of ˙O2-, h+ and ˙OH radicals. This study may be beneficial for the design of more efficient sunlight-driven hybrid photocatalysts and their applications in wastewater treatment.

Broad-spectrum absorption and highly effective charge-carrier separation are two essential requirements to improve the photocatalytic performance of semiconductor-based photocatalysts. In this work, a fascinating one-photon system is reported by rationally fabricating 2D in-plane Bi2O3/BiOCl (i-Cl) heterostructures for efficient photocatalytic degradation of RhB and TC. Systematic investigations revealed that the matched band structure generated an internal electric field and a chemical bond connection between the Bi2O3 and BiOCl in the Bi2O3/BiOCl composite that could effectively improve the utilization ratio of visible light and the separation effectivity of photo-generated carriers in space. The formed interactions at the 2D in-plane heterojunction interface induced the one-photon excitation pathway which has been confirmed by the experiment and DFT calculations. As a result, the i-Cl samples showed significantly enhanced photocatalytic efficiency towards the degradation of RhB and TC (RhB: 0.106 min−1; TC: 0.048 min−1) under visible light. The degradation activities of RhB and TC for i-Cl were 265.08 and 4.08 times that of pure BiOCl, as well as 9.27 and 2.14 times that of mechanistically mixed Bi2O3/BiOCl samples, respectively. This work provides a logical strategy to construct other 2D in-plane heterojunctions with a one-photon excitation pathway with enhanced performance.

Semiconductor hollow spheres have garnered significant attention in recent years due to their unique structural properties and enhanced surface area, which are advantageous for various applications in catalysis, energy storage, and sensing. The present study explores the surfactant-assisted synthesis of bismuth ferrite (BiFeO3) hollow spheres, emphasizing their enhanced visible-light photocatalytic activity. Utilizing a novel, facile, two-step evaporation-induced self-assembly (EISA) approach, monodisperse BiFeO3 hollow spheres were synthesized with a narrow particle size distribution. The synthesis involved Bi/Fe citrate complexes as precursors and the triblock copolymer Pluronic P123 as a soft template. The BiFeO3 hollow spheres demonstrated outstanding photocatalytic performance in degrading the emerging pollutants Rhodamine B and metronidazole under visible-light irradiation (100% degradation of Rhodamine B in <140 min and of metronidazole in 240 min). The active species in the photocatalytic process were identified through trapping experiments, providing crucial insights into the mechanisms and efficiency of semiconductor hollow spheres. The findings suggest that the unique structural features of BiFeO3 hollow spheres, combined with their excellent optical properties, make them promising candidates for photocatalytic applications.

Catalysts with S-scheme semiconductor junctions offers an enhanced redox capacity. Herein, BiOBr/Ag/Ag2S composites with a three-dimensional structure were prepared by hydrothermal reaction. The growth of Ag2S nanoparticles on the surface of BiOBr nanoflowers was successfully achieved, leading to strong light absorption and surface plasmon resonance (SPR) effect, together with improved rates of light-induced carriers. In the presence of peroxymonosulfate (PMS), the BiOBr/Ag/Ag2S composite removed 90.1 % of tetracycline (TC), outperforming BiOBr or Ag/Ag2S, owing to its superior redox capability and reduced carrier recombination efficiency. Additionally, BiOBr/Ag/Ag2S demonstrated excellent recovery performance and stability. Liquid chromatography-mass spectrometry (LC-MS) was employed to investigate the possible intermediate products and reaction pathways. The reaction mechanism of the S-scheme semiconductor heterojunction was further elucidated through density functional theory (DFT) calculations. In conclusion, the research provides a novel approach to activate PMS using an S-scheme semiconductor heterojunction with high redox capacity for practical use in wastewater treatment.

Solar energy is becoming the most promising option to mitigate the energy crisis in the future and can be applied in renewable and economical technologies such as water splitting and pollutants degradation. The promotion of the electronic energetic level is considered an efficient method to enhance the photocatalytic performance of semiconductor materials for solar energy conversion. The highly energetic electrons exhibit a remarkable reduction ability by virtue of the electronic spin polarization, which is associated with the conduction band (CB) position. Thus, the regulation of the CB position due to the redistribution of electrons by means of defect engineering presents potential. Here, a series of titanium-based metal-organic frameworks (Ti-based MOFs) named MIL-125-m% containing different extents of defects are reported to enable photocatalytic activity under simulated sunlight and visible light illumination for remarkably enhanced photocatalytic hydrogen evolution and pollutant degradation. The experimental results illustrated that MIL-125-5 % exhibited a superior photocatalytic hydrogen evolution rate (16507.27 μmol·g-1·h-1), much higher than that of MIL-125-0 % (1.444 μmol·g-1·h-1). The excellent photocatalytic performance was attributed to upshift of d-band center, which strengthened the adsorption of H*, facilitating the H2 evolution reaction. In addition, the degradation rate of MIL-125-5 % was up to twice the original rate, for the highly energetic electrons induced by the CB flexibility alleviated the photoinduced electron recombination in defective MIL-125. The strategy of defect engineering provides a new path to control the flexibility of the CB position by electronic spin polarization on adjustable metal-organic frameworks (MOFs), and the photocatalytic effect is changed accordingly.

The semiconductor-based photocatalysts with local surface plasmon resonance (LSPR) effect can extend light response to near-infrared region (NIR), as well as promote charge-carriers transfer, which provide a novel insight into designing light-driven photocatalyst with excellent photocatalytic performance. Here, we designed cost-effective wide-spectrum Zn2In2S5/W18O49 composite with enhanced photocatalytic performance based on a dual-channel charge transfer pathway. Benefiting from the synergistic effect of Z-scheme heterostructure and unique LSPR effect, the interfacial charge-carriers transfer rate and light-absorbing ability of Zn2In2S5/W18O49 were enhanced significantly under visible and NIR (vis-NIR) light irradiation. More reactive oxygen species (ROS) were formed by efficient molecular oxygen activation, which were the critical factors for both Escherichia coli (E. coli) photoinactivation and tetracycline (TC) photodegradation. The enhancement of molecular oxygen activation (MOA) ability was verified via quantitative analyses, which evaluated the amount of ROS through degrading nitrotetrazolium blue chloride (NBT) and p-phthalic acid (TA). By combining theoretical calculations with diverse experimental results, we proposed a credible photocatalytic reaction mechanism for antibiotic degradation and bacteria inactivation. This study develops a new insight into constructing promising photocatalysts with efficient photocatalytic activity in practical wastewater treatment.

The defectiveness of InGaN-based quantum wells increases with low indium contents, due to the compressive strain induced by the lattice mismatch between the InGaN and GaN layers, and to the stronger incorporation of defects favored by the presence of indium. Such defects can limit the performance and the reliability of LEDs, since they can act as non-radiative recombination centers, and favor the degradation of neighboring semiconductor layers. To investigate the location of the layers mostly subjected to degradation, we designed a color-coded structure with two quantum wells having different indium contents. By leveraging on numerical simulations, we explained the experimental results in respect of the ratio between the emissions of the two main peaks as a function of current. In addition, to evaluate the mechanisms that limit the reliability of this type of LED, we performed a constant-current stress test at high temperature, during which we monitored the variation in the optical characteristics induced by degradation. By comparing experimental and simulated results, we found that degradation can be ascribed to an increment of traps in the active region. This process occurs in two different phases, with different rates for the two quantum wells. The first phase mainly occurs in the quantum well closer to the p-contact, due to an increment of defectiveness. Degradation follows an exponential trend, and saturates during the second phase, while the quantum well close to the n-side is still degrading, supporting the hypothesis of the presence of a diffusive front that is moving from the p-side towards the n-side. The stronger degradation could be related to a lowering of the injection efficiency, or an increment of SRH recombination driven by a recombination-enhanced defect generation process.

Ionic polymeric carbon nitrides, poly(heptazine imides) (PHIs), have emerged as promising photocatalysts, yet the relationship between their structure, exciton dynamics, and activity has remained elusive so far. Here, a direct link is established between photocatalytic activity, spectroscopic properties, and theoretical analysis of structural effects on exciton behavior in water‐soluble PHIs with different cations. Using steady‐state and time‐resolved emission spectroscopy alongside ultrafast transient absorption spectroscopy performed in the absence and presence of hole and electron quenchers, two distinct excitonic relaxation pathways are uncovered: sub‐100 ps decay dominated by exciton recombination and shallow‐trap states, and sub‐ns dynamics associated with deep‐trap assisted recombination. Notably, ethanol accelerated the sub‐100 ps decay via hole quenching, while the deep traps are unaffected by ethanol. The spectroscopic results show that the photocatalytic activity in H2O2 production (CsPHI << NaPHI < KPHI) correlates with exciton lifetimes, whereby the theoretical analysis reveals that the observed modulation of exciton lifetimes is primarily related to different dark exciton dynamics governed by changes in interlayer interactions due to the altered structural corrugation in the presence of various cations. This work establishes a unified structure–dynamics–activity relationship in PHIs, offering new design guidelines for PHI‐based photocatalytic materials.

No abstract available

Noble-metal-decorated semiconductor photocatalysts have attracted noticeable attention due to their enhanced photocatalytic activity. Herein, we have synthesized the pure rutile phase of TiO2 nanorods, with microflower morphology, using a hydrothermal method and decorated them with Au to observe plasmon-induced enhanced photocatalytic efficiency. The optical bandgap engineering through Au-decorated TiO2 introduces midgap states that help with charge compensation during photodegradation studies. The surface plasmonic resonance peak of Au is observed together with the defect peak of TiO2, extending the absorption of the solar spectrum from the UV to the visible region. The quenching in photoluminescence intensity with increased Au thickness indicates the formation of a Schottky junction at the interface of Au and TiO2 that helps to reduce photogenerated charge carrier recombination. The softening of the E g Raman mode and photothermal effects originate from the nonradiative decay of localized surface plasmons through electron–phonon and phonon–phonon relaxation. The photocatalytic degradation of Rhodamine 6G is monitored by exposing the sample to UV and visible light sources under Raman spectroscopy. The Au decoration plays a crucial role in promoting charge separation, Schottky junction creation, photothermal effects, and UV to visible light absorption to enhance photocatalytic activity, which can be explained on the basis of the charge transfer mechanism. Our in-situ photodegradation study at the interface of noble metal and semiconducting materials will pave the way toward improving the understanding of plasmon-enhanced photocatalytic applications.

Cadmium telluride quantum dot (CdTe QD)-decorated graphene oxide (GO) nanosheets are promising heterojunctions for the environmental remediation of organic pollutants in water. However, assembling these two materials is a challenge. For this purpose, we have developed a one-step approach for the decoration of QDs onto the surface of GO nanosheets/intercalation of QDs into GO nanosheets through self-assembly, resulting in the formation of sandwiched hybrid heterojunctions. After synthesis, the samples were analysed for variations in their structural, morphological, compositional, optical and photoelectrochemical characteristics using various analytical tools. Interlinking QDs and GO nanosheets enhanced the photocurrent generation (∼5.8 μA cm-2), resulting in faster electron transfer by delaying the decay time (58.25 ms). A higher rate constant value (k = 0.135 min-1) was obtained for degrading 93% MB dye in 20 min. This work demonstrates a cost-effective strategy for constructing CdTe QDs/GO nanosheet hybrid heterojunctions for potential application in the field of photocatalysis.

No abstract available

No abstract available

Inspired by natural photosynthesis, the visible-light-driven Z-scheme system is very effective and promising for boosting photocatalytic hydrogen production and pollutant degradation. Here, a synergistic Z-scheme photocatalyst is constructed by coupling ReS2 nanosheet and ZnIn2S4 nanoflower and the experimental evidence for this direct Z-scheme heterostructure is provided by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and electron paramagnetic resonance. Consequently, such a unique nanostructure makes this Z-scheme heterostructure exhibit 23.7 times higher photocatalytic hydrogen production than that of ZnIn2S4 nanoflower. Moreover, the ZnIn2S4/ReS2 photocatalyst is also very stable for photocatalytic hydrogen evolution, almost without activity decay even storing for two weeks. Besides, this Z-scheme heterostructure also exhibits superior photocatalytic degradation rates of methylene blue (1.7 × 10-2 min-1) and mitoxantrone (4.2 × 10-3 min-1) than that of ZnIn2S4 photocatalyst. The ultraviolet-visible absorption spectra, transient photocurrent spectra, open-circuit potential measurement, and electrochemical impedance spectroscopy reveal that the superior photocatalytic performance of ZnIn2S4/ReS2 heterostructure is mostly attributed to its broad and strong visible-light absorption, effective separation of charge carrier, and improved redox ability. This work provides a promising nanostructure design of a visible-light-driven Z-scheme heterostructure to simultaneously promote photocatalytic reduction and oxidation activity.

The exploration of covalent organic frameworks (COFs) for high-efficiency photocatalytic CO2 reduction is urgently demanded. Herein, COF-based catalysts are constructed for the selective photoreduction of CO2 to CO via delicately designed isomeric monomers with substituent at the 4,5,9,10- positions (K) or 1,3,6,8-positions (A) of pyrene knots. The distinct substituted regions significantly affect the planarity of pyrene knots, resulting in COFs with different microstructures and photocatalytic activities. While employing a 5 W LED white-light as the light source, the single atomic Co contained A-Py-Bpy-COF-Co showcased a moderate CO evolution rate of 2174.4 µmol g-1 h-1. In sharp contrast, K-Py-Bpy-COF-Co reveals a considerable CO photo-reduction rate of 12 476.4 µmol g-1 h-1 (5.7 times higher than A-Py-Bpy-COF) with a selectivity up to 93.3%. Remarkably, the excellent photocatalytic activity of K-Py-Bpy-COF-Co can be maintained for at least 5 cycles without obvious decay. The distinct photocatalytic properties of the two isomeric COFs can be attributed to the larger steric-hindrance of K-Py-4CHO which enlarges the interlayer distances to inhibit exciton quenching and electron-richer nature of monatomic Co in K-Py-Bpy-COF-Co. This work provides a new protocol to explore COFs with boosted photocatalytic performance via isomeric design from refined modulation of reported COFs.

Linker-assisted Ag-TiO2 nanocomposite (NC)-based photocatalysts have been successfully synthesized using thioglycolic acid (TGA) and 3-mercaptopropionic acid (MPA) as bifunctional linker molecules (LMs). The Ag–LMs–TiO2 composites showed greatly improved photocatalytic performance for the degradation of an organic dye mixture under direct sunlight over bare Ag–TiO2 NCs. The efficiencies estimated from the degradation curves for Ag–TiO2, Ag–MPA–TiO2, and Ag–TGA–TiO2 are found to be 82.9%, 90.2%, and 96.1%, respectively. Compared to Ag–MPA–TiO2, Ag–TGA–TiO2 NCs exhibit an enhanced photocatalytic activity, which can be attributed to the TGA molecule's shorter chain length and, hence, faster and more charge transfer, which is duly confirmed by photoluminescence (PL) quenching and TRPL decay curves. Furthermore, higher Stern–Volmer quenching constant values (Ksv) have been obtained for Ag–TGA–TiO2 NCs compared to the bare Ag–TiO2 and Ag–MPA–TiO2 NCs from the PL quenching and estimated Ksv values for Ag–TiO2, Ag–MPA–TiO2, and Ag–TGA–TiO2 are 1400, 1950, and 2560 l−1, respectively. Interestingly, the Ag–TGA–TiO2 recycling analysis confirmed high stability and fast photodegradation up to 40 cycles. From the obtained results, it is concluded that the interfacial electron transfer kinetics in Ag–LM–TiO2 assemblies rely on the length of the alkyl-containing molecular linkers; the shorter the length, the more the charge transfer will be, thereby improving the photocatalytic behavior of the NCs.

Most of the photocatalytic reactions are currently driven by high-energy light (UV, blue light), which inevitably leads to side reactions and co-catalyst deactivation. Therefore, there is an urgent need to prepare novel photocatalysts with low-energy photocatalytic properties. Herein, we report a rational molecular design of covalent organic frameworks (COFs) equipped with donor-π-acceptor systems with different π-bridges (aromatic ring, mono- and bis-alkynyl). It was found that the COF with mono-alkynes as a π-bridge (TP-EDAE) can accelerate the rapid carrier migration even under low-energy light compared to the other two types of π-bridges (aromatic ring and bis-alkynyl), which was conducive to the photocatalytic redox reactions. As a result, the TP-EDAE samples showed high CO coupling activity and good substrate versatility under both high-energy light (blue light) and low-energy light (green light), especially the TP-EDAE samples displayed high stability with no obvious activity decay within five cycles under low-energy light. This work highlights the fundamental molecular design of advanced functionalized COFs with specific π-bridges for photocatalytic organic reactions under low-energy light.

Suppressing carrier recombination in bulk and facilitating carrier transfer to surface via rational structure design is of great significance to improve solar-to-H2 conversion efficiency. We demonstrate a facile hydrothermal method to synthesize porous SrTiO3 single crystals (SrTiO3-P) with exposed (001) facets by introducing carbon spheres as templates. The obviously increased surface photovoltage and photocurrent response indicate that the interconnected pore walls act as enormous charge transfer "highways", accelerating carrier transport from bulk to surface. Furthermore, the absence of grain boundaries and high crystallinity could also lower the carrier recombination rate. Thus, the SrTiO3-P photocatalyst loaded with Rh/Cr2O3 as cocatalyst exhibits 1.5 times higher overall water splitting activity than that of solid SrTiO3, with gas evolution rate of 19.99 μmol h-1 50 mg-1 for H2 and 11.37 μmol h-1 50 mg-1 for O2. Additionally, SrTiO3-P also shows superior stability without any decay during cycling testing. This work provides a new insight into designing efficient multicomponent photocatalysts with a single-crystal porous structure.

No abstract available

No abstract available

The S-scheme heterojunction photocatalyst holds potential for better photocatalysis owing to its capacity to broaden the light absorption range, ease electron-hole separation, extend the charge carrier lifespan, and maximize the redox ability. In this study, we integrate zeolitic imidazolate frameworks (ZIFs-67) with the CuFe-LDH composite, offering a straightforward approach towards creating a novel hybrid nanostructure, enabling remarkable performance in both photocatalytic hydrogen (H2) evolution and carbon dioxide (CO2) to methanol (MeOH) conversion. The ZIF-67/CuFe-LDH photocatalyst exhibits an enhanced photocatalytic hydrogen evolution rate of 7.4 mmol g-1 h-1 and an AQY of 4.8%. The superior activity of CO2 reduction to MeOH generation was 227 μmol g-1 h-1 and an AQY of 5.1%, and it still exhibited superior activity after continuously working for 4 runs with nearly negligible decay in activity. The combined spectroscopic analysis, electrochemical study, and computational data strongly demonstrate that this hybrid material integrates the advantageous properties of the individual ZIF-67 and CuFe-LDH exhibiting distinguished photon harvesting, suppression of the photoinduced electron-hole recombination kinetics, extended lifetime, and efficient charge transfer, subsequently boosting higher photocatalytic activities.

Ag–Fe bimetallic nanoparticles (alloy and core–shell structures) were synthesized using Grewia optiva leaf extract through a green, phytochemical‐mediated approach. The effects of pH, temperature, extract concentration, and Ag:Fe molar ratio on nanoparticle formation were systematically optimized, enabling size‐controlled and morphologically distinct nanostructures. Under optimized conditions (pH 8, 65°C, 3:1 Ag:Fe ratio), the nanoparticles exhibited strong optical properties and enhanced catalytic activity. Photocatalytic degradation of bromophenol blue (BPB) was performed using a 125‐W UV lamp (365 nm) for 90 min, and degradation efficiencies were calculated using absorbance decay following a pseudo–first‐order kinetic model. AgNPs, Ag–Fe alloy, and Ag–Fe core–shells achieved degradation efficiencies of 91%, 88.58%, and 81.47%, respectively. Postphotocatalysis Fourier transform infrared (FTIR), x‐ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed structural stability, and reusability tests demonstrated consistent catalytic performance over three cycles. These findings highlight the potential of G. optiva ‐mediated Ag–Fe nanostructures as cost‐effective and sustainable photocatalysts for dye degradation.

No abstract available

In this study, Bi-doped SrTiO3 perovskites (Sr1−xBixTiO3, x = 0, 0.03, 0.05, 0.07 and 0.1) were synthesized using the solid-state method, characterized, and tested as photocatalysts in the degradation of the azo dye acid orange 7 (AO7) under visible light. The perovskites were successfully synthesized, and XRD data showed a predominant, well-crystallized phase, belonging to the cubic perovskite symmetry. For the doped samples, a minority phase, identified as bismuth titanate, was detected. All doped samples exhibited improved photocatalytic activity under visible light, on the degradation of AO7 (10 mg L−1), when compared with the undoped SrTiO3, with an increase in relative Abs484 nm decay from 3.7% to ≥67.8% after 1 h, for a powder suspension of 0.2 g L−1. The best photocatalytic activity was exhibited by the Sr0.95Bi0.05TiO3 perovskite. Reusability studies showed no significant loss in photocatalytic activity under visible light. The final solutions showed no toxicity towards D. magna, proving the efficiency of Sr0.95Bi0.05TiO3 as a visible-light-driven photocatalyst to degrade both the AO7 dye as well as its toxic by-products. A degradation mechanism is proposed.

The photocatalytic activity of photocatalysts is severely hampered by limited visible light harvesting and unwanted fast recombination of photogenerated e− and h+. In the current study, the photocatalytic efficiency of Cu–ZnO/S-g-C3N4 (CZS) nanocomposites was investigated against MB dye. The composite materials were designed via chemical co-precipitation method and characterised by important analytical techniques. Distinctive heterojunctions developed between S-g-C3N4 and Cu–ZnO in the CZS composite were revealed by TEM. The synthesized composites exhibit a huge number of active sites, a large surface area, a smaller size and better visible light absorption. The considerable enhancement in the photocatalytic activity of CZS nanocomposites might be accredited to the decay in the e–h pair recombination rate and a red shift in the visible region, as observed by PL and optical analysis, respectively. Furthermore, the metal (Cu) doping into the S-g-C3N4/ZnO matrix created exemplary interfaces between ZnO and S-g-C3N4, and maximized the photocatalytic activity of CZS nanocomposites. In particular, CZS nanocomposites synthesized by integrating 25% S-g-C3N4 with 4% Cu–ZnO (CZS-25 NCs) exhibited the 100% photocatalytic degradation of MB in 60 minutes under sunlight irradiation. After six cycles, the photocatalytic stability of CZS-25 NCs was excellent. Likewise, a plausible MB degradation mechanism is proposed over CZS-25 NCs based on photoluminescence and reactive species scavenger test observation. The current research supports the design of novel composites for the photocatalytic disintegration of organic contaminants.

Effective separation of electron-hole and utilization of hot charge carriers are known to be the most important factors influencing the activity of a good photocatalyst. Herein, we developed a 1D/2D heterojunction in the composite of CdS nanorod and g-C3N4 (CN) nanosheets. These two form a quasi-type-II junction at the heterointerface. The photoexcited electrons are supposed to be transferred from CN to CdS, as observed from the enhanced photoluminescence of CdS. Transient studies revealed an absolute dominance of CdS exciton formation even in the composite system, although the dynamics were substantially modified in the presence of CN. The rise time of CdS band edge excitons were increased in the composite material, owing to the migration of hot electrons from CN to CdS. The hot electron transfer time was found to be ∼0.5 ps (rate constant ∼1.98 ps-1). The excitons decay in a much slower manner than that of the pristine CdS, confirming enhanced electron population in CdS. This migration of charge carriers was found to be immensely dependent on the applied excitation photon energy. Efficient migration of charge carriers leads to enhanced photocatalytic activity in the composite and an increased evolution of H2 evolution rate was witnessed. This detailed spectroscopic study toward the mechanistic pathway of the catalytic activity of an 1D/2D heterocomposite would be immensely helpful in fabricating many other effective heterojunctions which will advance the catalysis research.

Photoinduced hot carriers generated from the decay of surface plasmons in noble metals play a decisive role in producing green hydrogen gas through the photoelectrochemical (PEC) water splitting reaction, a process driven by visible light absorption. To optimize the utilization of these hot carriers, we employed a plasmonic antenna-reactor model based on core-shell structured Au@Pd nanoparticles (NPs) with an ultrathin Pd shell. In this study, we demonstrate that TiO2 nanotube arrays (TNAs) decorated with Au@Pd NPs exhibit superior performance with the Pd shell serving as a catalytic reactor that efficiently extracts hot carriers from the plasmonic Au antenna. The photocatalytic performance in PEC measurements increased with higher Pd coverage, and Au70@Pd30/TNAs exhibited a 2.2-fold higher photocurrent compared with bare Au/TNAs. The enhanced oxygen evolution reaction (OER) activity observed for Au70@Pd30/TNAs is attributed to the higher population of hot holes on the surface of Au@Pd NPs, which enhances the oxidation capability for interactions with electrolytes. Femtosecond transient absorption (fs-TA) spectra of Au@Pd NPs revealed a shorter lifetime of hot electrons through electron-phonon (e-p) scattering in Au70@Pd30 NPs compared to Au NPs, indicating suppressed charge recombination and increased hot hole population on the surface. Therefore, this study suggests that the plasmonic antenna-reactor model, critically influenced by hot carrier dynamics, provides a promising framework for efficient photoelectrocatalytic systems.

Solar light-induced catalysis has recently received great interest in efficiently and economically degrading volatile organic compounds, which deteriorate indoor and outdoor air quality. However, a few studies explored its essential photophysical and photochemical processes. Herein, the femtosecond transient absorption spectroscopy was used to investigate the decay of photogenerated holes in MnO2 with different Mn vacancies. About 67-93% of photogenerated holes recombined within a very short time (<130 ps), resulting in enhanced thermal catalytic activity of MnO2. Besides, really a small portion of photogenerated holes remained unchanged in the detection time period (1400 ps). ESR tests further confirm that photocatalytic pathway plays a significant role in degrading VOCs besides the thermal catalytic pathway when MnO2 is under illumination of UV-visible light. The introduction of an appropriate content of Mn vacancy did prolong the lifetime of photogenerated carriers. This work clarifies the mechanism of photoirradiation in improving the catalytic activity of MnO2 and the effect of manganese defects on the catalytic reaction.

The present study outlines the transformation of non-photoresponsive hexagonal boron nitride (HBN) into a visible-light-responsive material. The carbon modification was achieved through a solid-state reaction procedure inside a tube furnace under nitrogen atmosphere. In comparison to HBN (bandgap of 5.2 eV), the carbon-modified boron nitride could efficiently absorb LED light irradiation with a light harvesting efficiency of ≈90% and a direct bandgap of 2 eV. The introduction of carbon into the HBN lattice led to a significant change in the electronic environment through the formation of C–B and C–N bonds which resulted in improved visible light activity, lower charge transfer resistance, and improved charge carrier density (2.97 × 1019 cm−3). This subsequently enhanced the photocurrent density (three times) and decreased the photovoltage decay time (two times) in comparison to those of HBN. The electronic band structure (obtained through Mott–Schottky plots) and charge trapping analysis confirmed the dominance of e−, O2−•, and •OH as dominant reactive oxygen species. The carbon modification could effectively remove 93.83% of methylene blue (MB, 20 ppm solution) and 48.56% of phenol (10 ppm solution) from the aqueous phase in comparison to HBN which shows zero activity in the visible region.

A hollow spherical NiCo2S4 photocatalytic material was prepared with a high HER activity in the dye sensitization system. Then the hollow spherical NiCo2S4 was coated by the sheet-shaped 2D MoS2. Through the band gap adjustment, a type-II heterostructure is constructed to move the photogenerated electrons to the outer layer, and part of photogenerated holes migrate to the inner layer, which successfully reduces the degradation rate of the dye sensitizer for slowing down the decay of H2 evolution rate in the dye sensitization system. In addition, Ni2P was used to enrich photogenerated electrons on the outer layer of MoS2 thereby achieving more efficient hydrogen production. The photocatalytic materials were characterized by XRD, SEM, TEM, XPS, UV-vis DRS and N2 Isothermal adsorption experiments. The transfer mechanism of photogenerated carriers was studied by PL, photoelectrochemical tests, and hydroxyl radical capture experiments.

In this work, Fe2O3@TiO2 nanostructures with staggered band alignment were newly designed by an aerobic oil-phase cyclic magnetic adsorption method. XRD and TEM analyses were performed to verify the uniform deposition of Fe2O3 nanoparticles on the nanotube inner walls of TiO2. The steady-state degradation experiments exhibited that 1FeTi possessed the most superior performance, which might be ascribable to the satisfying dark adsorption capacity, efficient photocatalytic activity, ease of magnetic separation, and economic efficiency. These results indicated that the deposition of Fe2O3 into TiO2 nanotubes significantly enhanced the activity of Fe2O3, which was mainly ascribed to the Fe2O3-induced formation of staggered iron oxides@TiO2 band alignment and thus efficient separation of h+ and e−. Furthermore, the PL intensity and lifetime of the decay curve were considered as key criterions for the activity’s evaluation. Finally, the leaching tests and regeneration experiments were also performed, which illustrated the inhibited photodissolution compared with TiO2/Fe3O4 and stable cycling ability, enabling 1FeTi to be a promising magnetic material for photocatalytic water remediation.

Fundamental photocatalytic limitations of solar CO2 reduction remain due to low efficiency, serious charge recombination, and short lifetime of catalysts. Herein, two-dimensional graphitic carbon nitride nanosheets with nitrogen vacancies (g-C3 Nx ) located at both three-coordinate N atoms and uncondensed terminal NHx species were prepared by one-step tartaric acid-assistant thermal polymerization of dicyandiamide. Transient absorption spectra revealed that the defects in g-C3 N4 act as trapped states of charges to result in prolonged lifetimes of photoexcited charge carriers. Time-resolved photoluminescence spectroscopy revealed that the faster decay of charges is due to the decreased interlayer stacking distance in g-C3 Nx in favor of hopping transition and mobility of charge carriers to the surface of the material. Owing to the synergic virtues of strong visible-light absorption, large surface area, and efficient charge separation, the g-C3 Nx nanosheets with negligible loss after 15 h of photocatalysis exhibited a CO evolution rate of 56.9 μmol g-1  h-1 under visible-light irradiation, which is roughly eight times higher than that of pristine g-C3 N4 . This work presents the role of defects in modulating light absorption and charge separation, which opens an avenue to robust solar-energy conversion performance.

Cu2O, a narrow-bandgap semiconductor with visible light absorption capabilities, faces limitations in photocatalytic applications due to photocorrosion from hole self-oxidation and insufficient light absorption. In this work, a series of novel spherical Cu2O/FePO4 Z-scheme heterojunctions were successfully synthesized via self-assembly to overcome these challenges. The photocurrent, electrical impedance spectroscopy (EIS), and photoluminescence (PL) tests showed that Cu2O/1.5FePO4 (CF1.5) had excellent electron hole separation efficiency. Subsequently, photocatalytic degradation was utilized as a probing technique to further confirm the above conclusions, with the kinetic reaction constants of CF1.5 being 2.46 and 11.23 times higher than those of Cu2O and FePO4, respectively. After five cycles of experiments and XPS analysis, it was found that the content of Cu(I) in CF1.5 did not significantly decrease after the reaction, indicating that it has superior anti-photocorrosion performance compared to single Cu2O, which is also due to the establishment of a Z-scheme heterojunction. Systematic studies using radical scavenging experiments and ESR tests identified ·OH and ·O2− as the main active species involved in photocatalysis. The formation of a Z-scheme heterojunction not only enhances the photocatalytic activity of the CF1.5 composite but also effectively suppresses the photocorrosion of Cu2O, thereby offering a promising approach for enhancing anti-photocorrosion of Cu2O.

p-Cu2O is one of the most promising p-type semiconductor photocatalysts for the conversion of solar energy into chemical energy. However, the thermodynamically and kinetically permissible self-oxidation reaction of p-Cu2O leads to its low photostability, which remains a bottleneck for its practical application in photocatalysis. Herein, we have simultaneously inhibited thermodynamic and kinetic photocorrosion of p-Cu2O via constructing an amorphous hole-transfer conformal interface, which can maintain 91 % photocatalytic degradation efficiency at 6 cycles photodegradation of tetracycline (TC). The significantly improved photostability of the p-Cu2O is attributed to the formation of amorphous hole-transfer medium with a conformal shell structure on the surface of p-Cu2O, which can inhibit the thermodynamic self-oxidation of p-Cu2O by avoiding the contact between the photocatalyst and the electrolyte, and kinetically inhibit photocorrosion of p-Cu2O via accelerating hole transfer. These results should provide a fundamental solution to the photocorrosion of the photocatalysts, and open new opportunities for the design and development of photostable catalytic system.

No abstract available

Photoelectrochemical (PEC) water splitting that functions in pH-neutral electrolyte attracts increasing attention to energy demand sustainability. Here, we propose a strategy to in situ form a NiB layer by tuning the composition of the neutral electrolyte with the additions of nickel and borate species, which improves the PEC performance of the BiVO4 photoanode. The NiB/BiVO4 exhibits a photocurrent density of 6.0 mA cm−2 at 1.23 VRHE with an onset potential of 0.2 VRHE under 1 sun illumination. The photoanode displays a photostability of over 600 hours in a neutral electrolyte. The additive of Ni2+ in the electrolyte, which efficiently inhibits the dissolution of NiB, can accelerate the photogenerated charge transfer and enhance the water oxidation kinetics. The borate species with B─O bonds act as a promoter of catalyst activity by accelerating proton-coupled electron transfer. The synergy effect of both species suppresses the surface charge recombination and inhibits the photocorrosion of BiVO4.

No abstract available

Improving the charge transport and reducing the bulk/surface recombination are useful for improving the activity and stability of BiVO 4 for water oxidation. Here we for the first time demonstrate that the photoelectrochemical (PEC) performance of BiVO 4 can be significantly improved using the potentiostatically photo-polarized test. The co-catalyst-free BiVO 4 photoanode achieves a record-high photocurrent of 4.60 mA cm -2 at 1.23 V RHE with an outstanding onset potential of 0.23 V RHE in borate buffer without a sacrificial agent under AM 1.5G illumination. The most striking character is that the photoanode exhibits a strong "self-healing" property on photostability over 100 h under intermittent test. The synergistic effects of the generated oxygen vacancies and the passivated surface states at the semiconductor-electrolyte interface by the potentiostatically photo-polarized test reduces the substantial carrier recombination, and enhances the water oxidation kinetics, further inhibiting the photocorrosion.

Photoelectrochemical (PEC) water splitting using Ta3N5 anodes shows a high solar-to-hydrogen (STH) efficiency approaching 10%. However, the long-term stability of gas evolution should be improved for the commercial utilization of PEC water-splitting technology. Herein, we examined the photocurrent degradation of photoanodes prepared by uniformly loading a NiFeOx cocatalyst onto a Ta3N5 semiconductor. Although spectroscopic analysis showed that the degradation was attributable to the formation of an oxide layer, several oxide growth kinetic laws and mechanisms are known. We theoretically derived the photocurrent kinetic laws instead of the oxide growth kinetic laws by generalizing the Cabrera-Mott oxidation theory of metal oxidation in air to apply it to photocorrosion. The measured photocurrent kinetics are fully consistent with the theoretical kinetic laws. We show that ion drift due to charging of the oxide layer limits oxide growth even though uniform cocatalyst loading is designed to prevent self-oxidation of Ta3N5.

Photocorrosion of an n-type semiconductor is anticipated to be unfavorable if its decomposition potential is situated below its valence band-edge position. Tungsten trioxide (WO3) is generally considered as a stable photoanode for different photoelectrochemical (PEC) applications. Such oversimplified considerations ignore reactions with electrolytes added to the solvent. Moreover, kinetic effects are neglected. The fallacy of such approaches has been demonstrated in our previous study dealing with WO3 instability in H2SO4. In this work, in order to understand parameters influencing WO3 photocorrosion and to identify more suitable reaction environments, H2SO4, HClO4, HNO3, CH3O3SH, as electrolytes are considered. Model WO3 thin films are fabricated with a spray-coating process. Photoactivity of the samples is determined with a photoelectrochemical scanning flow cell. Photostability is measured in real time by coupling an inductively coupled plasma mass spectrometer to the scanning flow cell to determine the photoanode dissolution products. It is found that the photoactivity of the WO3 films increases as HNO3 < HClO4 ≈ H2SO4 < CH3O3SH, whereas the photostability exhibits the opposite trend. The differences observed in photocorrosion are explained considering stability of the electrolytes toward decomposition. This work demonstrates that electrolytes and their reactive intermediates clearly influence the photostability of photoelectrodes. Thus, the careful selection of the photoelectrode/electrolyte combination is of crucial importance in the design of a stable photoelectrochemical water-splitting device.

Heterogeneous catalysis composed of plasmonic metal and semiconductor has been utilized to tune local surface electron density in MOA (Molecular oxygen activation). However, there is a severe antagonistic effect between Schottky junction carriers and SPR (Surface Plasmon Resonance) induced hot carriers transfer routers when metal and semiconductor are both excited to dramatically reduce carriers separation efficiency. Hence, a highly effective photocatalytic antifoulant obtained by V-CN (carbon nitride with nitrogen vacancies) in-situ loading Cu2O and Ag nanoparticles (Cu2O/Ag/V-CN) was introduced to promote MOA to assist the metal ions sterilization. The DFT calculations (Density Functional Theory) and FEM calculations (Finite Element Method) intuitively proved the photocatalytic antifoulant belonged to a ternary Z-scheme heterojunction and could visibly weaken the antagonistic effect of hot carriers and Schottky carriers transport routes. The delocalized electron structure caused by V-CN and the effective electron mediator of Ag were the key to the formation of Z-scheme interfacial heterojunctions. These conclusions were also supported by experimental data, like more ∙O2- production capacity, efficient carriers separation, and higher carriers lifetime (27% higher than Cu2O and Cu2O/V-CN) as well as the weakened Cu2O photocorrosion tendency (Cu2O turning into CuO). Additionally, except for increasing nearly-three times adsorption energy of O2 for rapid activation, Cu2O/Ag/V-CN with abundant nitrogen vacancies can more significantly slow metal ions release (less about 97% to pure Cu2O and at least 22% higher than reported systems), which can observably save the amount of catalyst and heavy metals content. Therefore, Cu2O/Ag/V-CN has great potential for practical antifouling applications.

No abstract available

Semiconductor photocorrosion is a major challenge for the stability of photoelectrochemical water-splitting devices. Usually, photocorrosion is studied on the basis of thermodynamic aspects, by comparing the redox potentials of water to the self-decomposition potentials of the semiconductor or analyzing the equilibrium phases at given electrolyte conditions. However, that approach does not allow for a prediction of the decomposition rate of the semiconductor or the branching ratio with the redox reaction. A kinetic model has been developed to describe detailed reaction mechanisms and investigate competition between water-splitting and photocorrosion reactions. It is observed that some thermodynamically unstable semiconductors should photocorrode in a few minutes, whereas others are expected to operate over a period of years as a result of their extremely low photocorrosion current. The photostability of the semiconductor is mainly found to depend on surface chemical properties, catalyst activity, charge carrier density, and electrolyte acidity.

No abstract available

The efficiency of photoelectrochemical tandem cells is still limited by the availability of stable low band gap electrodes. In this work, we report a photocathode based on lithium doped copper(ii) oxide, a black p-type semiconductor. Density functional theory calculations with a Hubbard U term show that low concentrations of Li (Li0.03Cu0.97O) lead to an upward shift of the valence band maximum that crosses the Fermi level and results in a p-type semiconductor. Therefore, Li doping emerged as a suitable approach to manipulate the electronic structure of copper oxide based photocathodes. As this material class suffers from instability in water under operating conditions, the recorded photocurrents are repeatedly misinterpreted as hydrogen evolution evidence. We investigated the photocorrosion behavior of LixCu1-xO cathodes in detail and give the first mechanistic study of the fundamental physical process. The reduced copper oxide species were localized by electron energy loss spectroscopy mapping. Cu2O grows as distinct crystallites on the surface of LixCu1-xO instead of forming a dense layer. Additionally, there is no obvious Cu2O gradient inside the films, as Cu2O seems to form on all LixCu1-xO nanocrystals exposed to water. The application of a thin Ti0.8Nb0.2Ox coating by atomic layer deposition and the deposition of a platinum co-catalyst increased the stability of LixCu1-xO against decomposition. These devices showed a stable hydrogen evolution for 15 minutes.

No abstract available

No abstract available

No abstract available

Photocorrosion triggered by the unconsumed photogenerated holes severely deteriorates the photocatalytic efficiency and stability of semiconductor photocatalysts, especially in seawater with complex ions. Here, we report a hierarchical hollow ZnIn2S4 heterostructure integrating an inner CoOx nanocage and atomically dispersed Pt anchoring at surface S vacancies for hydrogen evolution from natural seawater (23.88 mmol g−1 h−1) and pure water (48.99 mmol g−1 h−1) under visible light. The dynamic Co2+/Co3+ self-reconstruction of the inner CoOx cage effectively consumes photogenerated holes, while the outer Pt1 single atoms localized at S vacancies serve as electron sinks to facilitate electron extraction and proton reduction. Benefiting from the dynamic hole-scavenging mechanism via oxidation self-reconstruction, the Pt1-ZnIn2S4@CoOX photocatalyst exhibits enhanced durability against alkali metal ions in seawater and maintains high reactivity for long-term hydrogen evolution. This work underscores the importance of light-induced transition metal dynamic self-reconstruction within hierarchical hollow heterostructure photocatalysts for sustainable hydrogen evolution. Photocorrosion caused by unreacted holes limits the performance of photocatalysts for photocatalytic seawater splitting. Here, the authors report that a hollow ZnIn2S4 structure with CoOx and Pt single atoms enables efficient, durable hydrogen production from seawater via dynamic self-reconstruction.

Cuprous oxide (Cu2O) is a promising photoelectrochemical (PEC) material, but its performance is hindered by poor charge separation and photocorrosion. These limitations can be effectively mitigated by constructing semiconductor heterojunctions that promote interfacial charge transfer and improve structural stability. Herein, we present a type-II Cu2O@Cu-HHTP core-shell heterostructure interface for highly efficient PEC sensing of H2S. The successful construction of the core-shell Cu2O@Cu-HHTP heterostructure is verified by material characterization. In particular, the new HR-TEM images reveal a sharp and coherent interface between the Cu2O and Cu-HHTP phases. The optimized interfacial charge transfer between Cu2O and the Cu-HHTP shell enables a markedly enhanced photocurrent of 3.81 μA, nearly five times higher than pristine Cu2O (0.84 μA). The resulting sensor exhibits an ultralow detection limit of 3.40 nM and an exceptionally broad linear range from 10.0 nM to 100.0 μM. Mechanism studies indicate that exposure to H2S forms Cu9S8 at the heterojunction, which disrupts its structure, accelerates charge recombination, and attenuates the photocurrent. Compared with existing sensing technologies, it demonstrates superior sensitivity and achieves the lowest detection limit reported to date among sensors based on metal oxides or MOFs materials. Enabling accurate detection of endogenous H2S in rat cerebrospinal fluid through in vivo microdialysis, demonstrating strong potential for biological monitoring. This work highlights an effective interfacial engineering strategy to boost charge separation and broaden detection capability, offering a robust platform for ultrasensitive PEC sensing of H2S in environmental and biomedical contexts.

The heterostructure WO3/BiVO4-based photoanodes have garnered significant interest for photoelectrochemical (PEC) solar-driven water splitting to produce hydrogen. However, challenges such as inadequate charge separation and photocorrosion significantly hinder their performance, limiting overall solar-to-hydrogen conversion efficiency. The incorporation of cocatalysts has shown promise in improving charge separation at the photoanode, yet mitigating photocorrosion remains a formidable challenge. Amorphous metal oxide-based passivation layers offer a potential solution to safeguard semiconductor catalysts. We examine the structural, surface morphological, and optical properties of two-step-integrated sputter and spray-coated TiO2 thin films and their integration onto WO3/BiVO4, both with and without NiOOH cocatalyst deposition. The J–V experiments reveal that the NiOOH cocatalyst enhances the photocurrent density of the WO3/BiVO4 photoanode in water splitting reactions from 2.81 to 3.87 mA/cm2. However, during prolonged operation, the photocurrent density degrades by 52%. In contrast, integrated sputter and spray-coated TiO2 passivation layer-coated WO3/BiVO4/NiOOH samples demonstrate a ∼88% enhancement in photocurrent density (5.3 mA/cm2) with minimal degradation, emphasizing the importance of a strategic coating protocol to sustain photocurrent generation. We further explore the feasibility of using natural mine wastewater as an electrolyte feedstock in PEC generation. Two-compartment PEC cells, utilizing both fresh water and metal mine wastewater feedstocks exhibit 66.6 and 74.2 μmol/h cm2 hydrogen generation, respectively. Intriguingly, the recovery of zinc (Zn2+) heavy metals on the cathode surface in the mine wastewater electrolyte is confirmed through surface morphology and elemental analysis. This work underscores the significance of passivation layer and cocatalyst coating methodologies in a sequential order to enhance charge separation and protect the photoanode from photocorrosion, contributing to sustainable hydrogen generation. Additionally, it suggests the potential of utilizing wastewater in electrolyzers as an alternative to freshwater resources.

Monoclinic PbCrO4 is an n-type semiconductor with a band gap of ∼2.2 eV, which has attracted research attentions as photoanode material for solar water splitting in recent years, but few works consider the correlation of PbCrO4 photoanodes' activity and stability with electrolytes. Herein, typical monoclinic PbCrO4 films were prepared by a drop-casting method and investigated as photoanodes for solar water splitting in sodium sulfate (NSO), phosphate-buffered saline (PBS), potassium bicarbonate (KHCO), sodium borate (NBO), and potassium hydrogen phthalate (KHP) aqueous electrolyte. The water oxidation activity of the PbCrO4 film photoanode was found to be closely related to the electrolyte, and a relatively higher activity was observed on the PbCrO4 photoanode in PBS and KHP. However, in the five types of electrolytes, the PbCrO4 film photoanode had unsatisfactory stability due to the presence of photocorrosion, composition transformation, and dissolution, posing a significant challenge to the application of PbCrO4 in solar water splitting. In the Na2SO3/KHP mixing electrolyte, improved and stable photocurrent can be achieved on the PbCrO4 film photoanode for the oxidation of SO32- into SO42-. The present work reveals the objective water splitting behaviors of the PbCrO4 film photoanode in typical electrolytes, which could provide helpful reference and act as a reminder for the research of PbCrO4 and similar photoanode materials.

Light-driven water electrolysis at a semiconductor surface is a promising way to generate hydrogen from sustainable energy sources, but its efficiency is limited by the performance of available photoabsorbers. Here we report the first time investigation of covalent organic frameworks (COFs) as a new class of photoelectrodes. The presented 2D-COF structure is assembled from aromatic amine-functionalized tetraphenylethylene and thiophene-based dialdehyde building blocks to form conjugated polyimine sheets, which π-stack in the third dimension to create photoactive porous frameworks. Highly oriented COF films absorb light in the visible range to generate photoexcited electrons that diffuse to the surface and are transferred to the electrolyte, resulting in proton reduction and hydrogen evolution. The observed photoelectrochemical activity of the 2D-COF films and their photocorrosion stability in water pave the way for a novel class of photoabsorber materials with versatile optical and electronic properties that are tunable through the selection of appropriate building blocks and their three-dimensional stacking.

Photoelectrochemistry (PEC) represents an alternative approach for a sustainable production of hydrogen (H2) or high-value chemicals compared to light absorption by photovoltaic systems and subsequent water electrolysis. Both steps are combined into a single integrated device, which can potentially reduce costs. It further allows for decoupling from the electric grid, enabling operation in remote areas. Currently, however, the efficiency is still comparatively poor and the cost high, impeding an implementation of PEC devices on an industrial scale. Optimization strategies consist of improving light absorption and charge separation in the semiconductor absorbers often by creating multijunction systems combining several materials, and by developing non-noble metal catalysts that are deposited on the electrode surface and improve the charge extraction and conversion efficiencies. Apart from insufficient conversion efficiencies, a major problem arises from photocorrosion. Since the photoelectrode is in direct contact with the electrolyte, degradation of many state-of-the-art absorber systems, such as III-V semiconductors, is observed, raising the necessity for the development of additional protection layers, further complicating the electrode design.[1] [2] MoS2 has emerged as an earth-abundant – and thus cost-effective – layered catalyst material that can efficiently act as both the protective coating and the catalyst, and allows for long-term operation on the order of weeks to months.[3] [4] Most of these results were obtained in lab-scale experiments, however, relying on a high control of experimental parameters. While this strategy is suitable in terms of material optimization and stack design, it does not represent the conditions relevant to real-world operation outdoors, which are a lot less controlled and more variable as they fall victim to changes in weather and varying illumination intensity.[5] [6] Thus, perceived understandings of stability and activity might only be applicable to a lesser extent, demanding further studies. In the case of MoS2, catalyst corrosion slowly occurs at the open circuit voltage (OCV) – which notably reflects nocturnal conditions, and can thus be detrimental for long-term stability.[7] In order to improve the stability without a loss of activity, more insights are needed to understand dissolution mechanisms and material characteristics. Presumedly, the most severe MoS2 dissolution occurs via oxidation at the active sites, as these provide undercoordinated Mo-sites and S-dangling bonds.[8] [9] Thus, a thorough understanding and control of the active site density in any MoS2 catalyst is required. In this work we deposited Mo thin-films on Si using physical vapor deposition and varied the temperature and duration during the subsequent sulfidation process in 10 % H2S. Activity and stability (especially at OCV) are then characterized via cyclic voltammetry (CV), inductive coupled plasma mass spectrometry (ICP-MS), and evaluation of the electrochemical active surface area. This allows for a comparative analysis of structure-activity-stability correlations, and thus the development of optimum synthesis conditions. Ultimately, the question is if it is possible to prepare a truly stable and still active MoS2 layer that can be used as catalyst and protective coating for long-term real-world PEC application. Finally, strategies to improve the stability of MoS2-covered photoelectrodes towads this goal will be discussed. REFERENCES [1] D. Tilley, J. Moon, Chem. Soc. Rev. 2019, 48, 4979. [2] J. Zheng, H. Zhou, Y. Zou, R. Wang, Y. Lyu, S. P. Jiang, S. Wang, Energy Environ. Sci. 2019, 12, 2345–2374. [3] L. A. King, T. R. Hellstern, J. Park, R. Sinclair, T. F. Jaramillo, ACS Appl. Mater. Interfaces 2017, 9, 36792–36798. [4] M. Ben-Naim, C. W. Aldridge, M. A. Steiner, R. J. Britto, A. C. Nielander, L. A. King, T. G. Deutsch, J. L. Young, T. F. Jaramillo, ACS Appl. Mater. Interfaces 2021, 14, 1–8. [5] K. M. K. Yap, S. A. Lee, T. A. Kistler, D. K. Collins, E. L. Warren, H. A. Atwater, T. F. Jaramillo, C. Xiang, A. C. Nielander, 2024, 1–11. [6] F. Nandjou, S. Haussener, E. D. Electro-deposition, J. Phys. D. Appl. Phys. 2017, 50, 124002. [7] Z. Wang, Y. R. Zheng, J. Montoya, D. Hochfilzer, A. Cao, J. Kibsgaard, I. Chorkendorff, J. K. Nørskov, ACS Energy Lett. 2021, 6, 2268–2274. [8] I. G. Vasilyeva, I. P. Asanov, L. M. Kulikov, J. Phys. Chem. C 2015, 119, 23259–23267. [9] P. Afanasiev, C. Lorentz, J. Phys. Chem. C 2019, 123, 7486–7494.

Photoelectrochemical (PEC) water splitting offers a promising solution for solar-to-hydrogen energy conversion. However, slow charge transfer and severe photocorrosion limit the activity and stability. To break the activity-stability trade-off, we developed a highly conductive and structurally stable three-dimensional (3D) porous network hydrogel (Gel) via cross-linking polyaniline (PANI) and poly(acrylic acid) (PAA). Functional groups within the Gel anchor metal ions, enabling the synthesis of a P(ANI-AA)-CoFe dual-functional layer, where CoFe is chemically bonded to the hydrogel network. The Gel-CoFe coupled with NiO hole transfer layer, was integrated onto semiconductor metal oxide (MO: TiO2, Fe2O3, WO3, and BiVO4) arrays, forming Gel-CoFe/NiO/MO photoanodes. Especially, the P(ANI-AA)-CoFe/NiO/BiVO4 photoanode achieves a high photocurrent density of 6.26 mA cm-2 at 1.23 V vs RHE. Moreover, a large-scale P(ANI-AA)-CoFe/NiO/BiVO4 system sustains a photocurrent of 27 mA with 500 h long-term operational stability at 1.1 V vs RHE, outperforming previously reported PEC systems. The porous 3D framework suppresses photocorrosion and facilitates the transport of reactive species, whereas the high conductivity and abundant active sites enhance interfacial charge mobility. This rationally designed hydrogel-catalyst dual-network establishes a universal and extendable paradigm overcoming durable activity-stability trade-off in PEC system.

No abstract available

No abstract available

No abstract available

The physicochemical properties of a semiconductor surface, especially in low-dimensional nanostructures, determine the electrical and optical behavior of the devices. Thereby, the precise control of surface properties is a prerequisite for not only preserving the intrinsic material quality but also manipulating carrier transport behavior for promoting device characteristics. Here, we report a facile approach to suppress the photocorrosion effect while boosting the photoresponse performance of n-GaN nanowires in a constructed photoelectrochemical-type photodetector by employing Co3O4 nanoclusters as a hole charging layer. Essentially, the Co3O4 nanoclusters not only alleviate nanowires from corrosion by optimizing the oxygen evolution reaction kinetics at the nanowire/electrolyte interface but also facilitate an efficient photogenerated carrier separation, migration, and collection process, leading to a significant ease of photocurrent attenuation (improved by nearly 867% after Co3O4 decoration). Strikingly, a record-high responsivity of 217.2 mA W-1 with an ultrafast response/recovery time of 0.03/0.02 ms can also be achieved, demonstrating one of the best performances among the reported photoelectrochemical-type photodetectors, that ultimately allowed us to build an underwater optical communication system based on the proposed nanowire array for practical applications. This work provides a perspective for the rational design of stable nanostructures for various applications in photo- and biosensing or energy-harvesting nanosystems.

Developing low‐cost, high‐performance, and durable photoanodes is essential in solar‐driven photoelectrochemical (PEC) energy conversion. Sb2S3 is a low‐bandgap (≈1.7 eV) n‐type semiconductor with a maximum theoretical solar conversion efficiency of ≈28% for PEC water splitting. However, bulk Sb2S3 exhibits opaque characteristics and suffers from severe photocorrosion, and thus the use of Sb2S3 as a photoanode material remains underexploited. This study describes the design and fabrication of a transparent Sb2S3‐based photoanode by conformably depositing a thin layer of conjugated polycarbazole frameworks (CPF‐TCzB) onto the Sb2S3 film. This structural design creates a type‐II heterojunction between the CPF‐TCzB and the Sb2S3 with a suitable band‐edge energy offset, thereby, greatly enhancing the charge separation efficiency. The CPF‐TCzB/Sb2S3 hybrid photoanode exhibits a remarkable photocurrent density of 10.1 mA cm−2 at 1.23 V vs reversible hydrogen electrode. Moreover, the thin CPF‐TCzB overlayer effectively inhibits photocorrosion of the Sb2S3 and enables long‐term operation for at least 100 h with ≈10% loss in photocurrent density. Furthermore, a standalone unbiased PEC tandem device comprising a CPF‐TCzB/Sb2S3 photoanode and a back‐illuminated Si photocathode can achieve a record solar‐to‐hydrogen conversion efficiency of 5.21%, representing the most efficient PEC water splitting device of its kind.

Photoelectrochemical (PEC) reduction of CO2 into chemical fuels and chemical building blocks is a promising strategy for addressing the energy and environmental challenges, which relies on the development of p-type photocathode. Cu2O is such a p-type semiconductor for photocathode but commonly suffers from detrimental photocorrosion and chemical changes. In this communication, we develop a facile procedure for coating metal-organic framework (MOF) on the surface of Cu2O photocathode, which can both prevent photocorrosion and offer active sites for CO2 reduction. As evidenced by ultrafast spectroscopy, the formed interface can effectively promote charge separation and transfer. As a result, both the activity and durability of Cu2O are dramatically enhanced for PEC CO2 reduction. This work provides fresh insights into the design of advanced hybrid photoelectrodes and highlights the important role of interfacial charge kinetics in PEC CO2 conversion.

No abstract available

In this research, for the first time, the synthesis of nanostructure of zeolitic imidazolate framework-11/graphitic carbon nitride (ZIF-11/g-C_3N_4 X) with different weight of g-C_3N_4 (X: 0.01, 0.1, 0.3 g) is reported. Their performance was compared in photocatalytic degradation of MB under visible light. Synthetic samples were characterized by X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometer (XPS), diffused reflectance spectroscopy (DRS), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET), Electrochemical Impedance Spectroscopy (EIS) and Photoluminescence (PL) analysis. Based on the results, Z-scheme ZIF-11/g-C_3N_4 0.3 was selected as the best sample. FESEM and TEM images indicated that g-C_3N_4 sheets were complicated on the surface of ZIF-11 with rhombic dodecahedron (RHO) morphology. The surface area and band gap of ZIF-11/g-C_3N_4 0.3 was determined as 174.5 m^2/g and 2.58 eV, respectively. The recombination of charge carriers in the ZIF-11/g-C_3N_4 0.3 nanostructure was reduced. Photocatalytic degradation efficiency of MB (5 ppm), pH = 7, visible irradiation (120 W-60 min) using 0.1 g of ZIF-11/g-C_3N_4 0.3 was achieved 72.7% with first-order kinetic model and acceptable stability in three consecutive cycles. Further, the total organic carbon (TOC) removal rate by ZIF-11/g-C_3N_4 0.3 after 5 h were 66.5%.

Two-dimensional transition metal dichalcogenides experience degradation in optoelectronic properties under ambient conditions. By performing non-adiabatic (NA) molecular dynamics simulations, we demonstrate that MoS2 monolayer containing substitutional oxygen and oxygen adatom accelerates nonradiative electron-hole recombination by a factor of about 1.5 compared to perfect film but operates by different mechanisms. The substitutional oxygen creates no mid-gap states while enhances NA coupling by increasing the overlap between electron and hole wave functions, accelerating electron-hole recombination. In contrast, electrons significantly populate the deep trap state created by the oxygen adatom because the trap is modestly delocalized and coupled strongly to free charges. Trap mediated instead of direct pathway dominates the electron-hole recombination. The generated insights uncover the mechanisms for different types of defects on influencing charge dynamics in TMDs, and suggest the oxygen defects should be avoided for design of high-performance optoelectronic devices.

No abstract available

Making full use of low-energy photons and reducing photogenerated carriers' recombination rate have been considered important ways to raise photoelectrocatalysis (PEC) efficiency. In this study, Ir-doped ZnO PEC electrodes were prepared by thermal decomposition method, first principles calculations were used to study the effects of Ir content on the electronic structure and optical properties of IrxZn1-xO coatings, the PEC degradation mechanism of the IrxZn1-xO/Ti electrodes was also tentatively presented. The results indicated that with numbers of Zn atoms replaced by Ir atoms, impurity energy level appeared in ZnO band gap, which reduced the electron transition barriers and increased the number of photogenerated carriers. Besides, IrO2 nanoparticles covered on ZnO nanorods surface, acting as highly efficient electron transfer channels and electrocatalytic active sites, could separate photogenerated electron-hole pairs and enhance PEC performance effectively. PEC performance of IrxZn1-xO/Ti electrodes with different Ir contents under UV irradiation was evaluated by rhodamine B (RhB) removal rate. Compared with pure ZnO electrodes, IrxZn1-xO/Ti ones exhibited much stronger degradation capacity. Specifically, Ir0.09375Zn0.90625O/Ti electrodes showed the highest degradation rate of 99.4 %, and a relatively high rate of 95.2 % after working 100 h continuously, indicating its excellent long-term stability.

Photocatalytic technology has emerged as a promising solution to global water contamination, mainly through the effective degradation of persistent pharmaceutical pollutants. However, a few challenges still exist in enhancing degradation efficiency, reducing the toxicity of by-products, and ensuring cost-effective scalability. This study focuses on Tetracycline Hydrochloride (TCH) as an index antibiotic pollutant to evaluate the performance of a novel MXene-derived TiO2-supported SiO₂/ Ti3C2 composite (SMXT) synthesised using ultrasonic and wet impregnation techniques. The SMXT-450 sample, annealed at 450°C, exhibited a remarkable 95% degradation of TCH within 80 minutes, surpassing more complex three-component systems. The superior photocatalytic activities, validated through comprehensive characterisation tests, were found to stem from an optimised band gap, minimised electron-hole recombination, and enhanced charge transfer. The effective degradation process, primarily driven by •O₂⁻ and •OH radicals, was confirmed by trapping and ESR analysis. High-performance liquid chromatography (HPLC) and toxicity assessments also revealed that the intermediate degradation products are less harmful, further demonstrating the environmental sustainability of the formulated nanocomposites in treating antibiotic-polluted waters. This study's findings can highlight the potential of MXene-derived nanocomposites for the efficient remediation of antibiotic-contaminated water, offering a cost-effective and scalable approach to mitigating the impact of pharmaceutical pollutants on aquatic ecosystems.

This project presents the fabrication of an efficient heterojunction photocatalyst through combining 3D MoS2 nanoflowers with 2D MoO3 nanobelts, both having highly prominent photocatalytic features. The prepared MoS2@MoO3 heterojunction exhibited superior photocatalytic activity towards the degradation of Azo dye under visible light irradiation and attained about 96% degradation within four hours. Such a high photocatalytic activity might be associated with the high BET surface area, and especially with the S-scheme mechanism that occurs between p-type MoS2 and p-type MoO3, probably due to the fact that this offers effectively separated and transitioned photogenerated electron-hole pairs, while the recombination rate is reduced. The addition of MoO3 increased the bandgap of MoS2 and consequently enhanced the photoinduced electron transfer rate and prolonged the lifetime of the charge carriers. In a word, the generation of hole and •O2– radicals in the whole process of degradation, which have been proved by scavenger tests and Mott-Schottky analysis, proved the MoS2@MoO3 p-p heterojunction to be photocatalytically active. This work underlines the successful application of bandgap and morphological engineering in the design of photocatalysts and points out the 3D/2D MoS2@MoO3 heterojunction structure as the basis for further development of transition metal chalcogenide (TMC)/transition metal oxide (TMO) photocatalysts with a view to tackling important environmental problems by means of sustainable technologies.

Fluorinated organic pollutants pose significant environmental and health risks due to the high stability of C-F bonds, necessitating effective strategies for their degradation. Herein, we present a bilayer WO3 photoelectrode (double-WO3) incorporating an electron transport layer (ETL) and a hexagonal-monoclinic heterophase junction for PEC degradation of fluorinated pollutants. The double-WO3 catalyst achieves a high photocurrent density (4.3 mA cm-2 at 1.2 VRHE) and nearly complete degradation (99.9%) of bisphenol AF (BPAF), 4-fluorophenol (4-FP), and pentafluorophenol (PFP), with 99.9% mineralization of PFP. Experimental and transient photocurrent (TPC) analyses confirm that the ETL-heterophase junction structure enhances electron extraction and surface reaction kinetics while minimizing electron-hole recombination. In this process, photogenerated h+ excites fluorinated pollutants, enhancing C-F bond susceptibility to ∙OH attack, which facilitates bond cleavage and subsequent oxidation into CO2, H2O, and F-. This study offers a promising strategy for designing advanced PEC systems and effectively remediating persistent fluorinated contaminants.

Exploring efficient photocatalysts for the degradation of VOCs under visible light is a challenge. CdS@g-C3N4 heterojunction photocatalytic materials were developed in this study using a microwave-assisted sol-gel process. CdS@g-C3N4(0.2) photocatalyzed the maximum degradation of gaseous toluene under visible light irradiation, and the time required to achieve the same degradation rate was reduced by 270 min when compared to pure CdS. The morphological characterization, photoelectric property analysis, and DFT calculations all verified that the CdS nanoparticles were uniformly disseminated on the surface of g-C3N4, and that the interfaces were closely contacted to form a heterojunction interface with a built-in field. This enhances charge transfer from CdS to g-C3N4 while successfully decreasing electron-hole pair recombination caused by light. Furthermore, the energy band structure was altered to absorb longer wavelengths of light and extend the absorption spectral range, improving the photocatalytic material's efficacy for broad-spectrum light such as sunshine. This paper proposes methods for predicting and optimizing the surface structure of catalysts, as well as developing high-performance multi-heterojunction photocatalysts for the degradation of indoor VOCs.

The current study focuses on boosting the photocatalytic ability of reduced graphene oxide (rGO) by decorating the rGO nano-sheets with nickel oxide (NiOx) and silver (Ag) nanomaterials. The developed ternary nanomaterials were investigated using FTIR, XRD, FESEM, TEM, Raman, and UV-vis to evaluate the photo-degradation process. The rGO/NiOx/Ag ternary system showed promising photocatalytic dye degradation under simulated sunlight irradiance. The addition of NiOx and Ag nanomaterials widened the catalytic activity spectrum from the visible region to the UV-region. Besides, these materials hindered the electron–hole recombination, boosting the catalytic activity. The reusability results also clearly showed that the synthesized ternary nanomaterials have good reproducibility and stability for photocatalytic degradation of industrial wastewater.

BiOI is a promising photocatalyst due to its exceptional visible light response and high absorption coefficient; however, its performance is hindered by the rapid recombination of electron-hole (e--h+) pairs. Herein, a 2D/3D BiOI/g-C3N4 S-scheme heterojunction catalyst was designed and constructed through the alkali etching strategy and subsequent microwave-assisted hydrothermal strategy. The abundant surface active sites and matched band gap of g-C3N4 prepared through alkali etching facilitates anchoring of BiOI nanosheets, contact with contaminants and construction of heterojunctions. 2D/3D S-scheme heterojunction substantially promote electron-hole (e--h+) pairs separation and transfer. Profited from their synergistic effects, the 2D/3D BiOI/g-C3N4 heterojunction delivers superior photocatalytic activity toward four different types of pollutants: methylene blue (91.7 %), tetracycline (91.9 %), eosin y (90.9 %) and methyl orange (97.7 %), and demonstrates excellent cyclic stability after seven methylene blue cyclic degradation experiments. Furthermore, BiOI/g-C3N4 has shown satisfactory practicability in many simulation experiments, such as coexisting cations, different pH and real water. A feasible strategy to prepare a visible-light-driven multidimensional coordinated S-scheme heterojunction photocatalyst is provided in this work.

No abstract available

In the present work, the photodegradation of Rhodamine B with different pH values by using Bi2O3 microrods under visible-light irradiation was studied in terms of the dye degradation efficiency, active species, degradation mechanism, and degradation pathway. X-ray diffractometry, polarized optical microscopy, scanning electron microscopy, fluorescence spectrophotometry, diffuse reflectance spectra, Brunauer–Emmett–Teller, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, UV–visible spectrophotometry, total organic carbon, and liquid chromatography–mass spectroscopy analysis techniques were used to analyze the crystal structure, morphology, surface structures, band gap values, catalytic performance, and mechanistic pathway. The photoluminescence spectra and diffuse reflectance spectrum (the band gap values of the Bi2O3 microrods are 2.79 eV) reveals that the absorption spectrum extended to the visible region, which resulted in a high separation and low recombination rate of electron–hole pairs. The photodegradation results of Bi2O3 clearly indicated that Rhodamine B dye had removal efficiencies of about 97.2%, 90.6%, and 50.2% within 120 min at the pH values of 3.0, 5.0, and 7.0, respectively. In addition, the mineralization of RhB was evaluated by measuring the effect of Bi2O3 on chemical oxygen demand and total organic carbon at the pH value of 3.0. At the same time, quenching experiments were carried out to understand the core reaction species involved in the photodegradation of Rhodamine B solution at different pH values. The results of X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffractometer analysis of pre- and post-Bi2O3 degradation showed that BiOCl was formed on the surface of Bi2O3, and a BiOCl/Bi2O3 heterojunction was formed after acid photocatalytic degradation. Furthermore, the catalytic degradation of active substances and the possible mechanism of the photocatalytic degradation of Rhodamine B over Bi2O3 at different pH values were analyzed based on the results of X-ray diffractometry, radical capture, Fourier-transform infrared spectroscopy, total organic carbon analysis, and X-ray photoelectron spectroscopy. The degradation intermediates of Rhodamine B with the Bi2O3 photocatalyst in visible light were also identified with the assistance of liquid chromatography–mass spectroscopy.

Mixed Sn-Pb perovskites are attracting significant attention due to their narrow bandgap and consequent potential for all-perovskite tandem solar cells. However, the conventional hole transport materials can lead to band misalignment or induce degradation at the buried interface of perovskite. Here we designed a self-assembled material 4-(9H-carbozol-9-yl)phenylboronic acid (4PBA) for the surface modification of the substrate as the hole-selective contact. It incorporates an electron-rich carbazole group and conjugated phenyl group, which contribute to a substantial interfacial dipole moment and tune the substrate's energy levels for better alignment with the Sn-Pb perovskite energy levels, thereby promoting hole extraction. Meanwhile, enhanced perovskite crystallization and improved contact at bottom of the perovskite minimized defects within perovskite bulk and at the buried interface, suppressing non-radiative recombination. Consequently, Sn-Pb perovskite solar cells using 4PBA achieved efficiencies of up to 23.45%. Remarkably, the 4PBA layer provided superior interfacial chemical stability, and effectively mitigated device degradation. Unencapsulated devices retained 93.5% of their initial efficiency after 2000 h of shelf storage.

We present a novel approach for enhancing photocatalytic efficiency by developing polyaniline (PANI) and polyindole (PIN)-coated TiO2 nanotubes (TNT) through a combination of chemical oxidation and hydrothermal processes. The PANI–PIN coating was systematically applied to both the internal and external surfaces of the nanotubes to enhance the photocatalytic active sites and optimize pollutant adsorption. The dual-coated structure enhances the interaction with pollutants, facilitating a more efficient degradation of 4-nitrophenol (4-NP) when exposed to visible light. Thorough characterization through X-ray diffraction (XRD), Fourier-transform infrared (FTIR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), N2-physisorption, transient photocurrent, diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) validated the exceptional structural and optical properties of the composite. The PANI/PIN polymer coating effectively inhibited electron–hole recombination, leading to a notable enhancement in photocatalytic performance. Among the tested composites, the formulation consisting of 75% PANI and 25% PIN demonstrated remarkable performance, achieving a degradation rate of 99.46% for 4-NP in only 120 min of exposure to visible light. The impressive efficiency stems from its extensive surface area (255.3 m2/g), efficient charge separation, minimized band gap (2.77 eV), and improved light absorption. Moreover, the composite demonstrated remarkable recyclability, preserving its catalytic activity across five cycles without any decline in performance. These results demonstrate the strong potential of 75%PPTN as a promising photocatalyst for environmental remediation.

TiO2 has the proven capability of catalytically decomposing pollutants under light illumination, thereby embracing potential applications in wastewater management. The photocatalytic dye degradation activity is largely controlled by the optical band gap that dictates the extent of electron-hole pair generation via photon absorption, and the recombination kinetics of charges. In this context, the material's work function governs how easily the charge carriers can be transferred at the dye-adsorbed photocatalytically active sites. Accordingly, nanocrystalline TiO2 thin films are grown in the anatase phase with ⟨101⟩ orientation, using RF magnetron sputtering at 200 °C. Besides studying the film's structural morphology, optical band gap, and elemental composition, the electronic properties are extensively investigated. The work function of the material was controlled by varying the O-vacancy-dependent Ti3+ bonding configuration in the network. It has been demonstrated how the photocatalytic methylene blue dye degradation activity of the nanocrystalline TiO2 films of predominantly the anatase phase improves on reducing the sputtering pressure during deposition. At a low deposition pressure of 20 mTorr, a low work function of ∼4.2 eV of the film, resulting from the formation of a Ti3+-bond through the O vacancies in the network, potentially increases its carrier lifetime and delivers the superior photocatalytic activity (∼82.7% dye degradation with a rate constant of k ∼ 0.0073 min-1) via silently facilitating fast electron transfer from the photocatalyst to the dye in the aqueous solution. The higher stoichiometric film prepared at p = 40 mTorr exhibits an inferior photocatalytic activity (∼20.4% dye degradation with a rate constant of k ∼ 0.0009 min-1), as retarded by its higher work function of ∼4.62 eV, despite retaining a relatively low band gap. Thus, without using any heterojunction or extrinsically doped photocatalyst, the dye degradation can be controlled simply by reducing the work function of nanocrystalline TiO2 thin films via controlling the O-vacancy-dependent Ti3+ bonding in its self-doped network.

Recent research on SnS2 materials aims to enhance their photocatalytic efficiency for water pollution remediation through doping and constructing heterojunctions. These methods face challenges in cost-effectiveness and practical scalability. This study synthesizes hexagonal SnS2 nanosheets of various sizes via a hydrothermal method, assessing their performance in degrading methyl orange (MO) and reducing hexavalent chromium (Cr(VI)). The results show that smaller SnS2 nanosheets exhibit higher photocatalytic efficiency under sunlight. Specifically, 50 mg of small-sized nanosheets degraded 100 ml of MO (10 mgL-1) in 30 min and reduced Cr(VI) (10 mgL-1) in 105 min. The enhanced performance is attributed to: i) an energy bandgap of 2.17 eV suitable for visible light, and ii) more surface sulfur (S) vacancies in smaller nanosheets, which create electronic states near the Fermi level, reducing electron-hole recombination. This study offers a straightforward strategy for improving 2D materials like SnS2.

Organometallic surface functionalization of colloidal CdSe and CdS nanocrystals using iron tetracarbonyl moieties is demonstrated to enable study of in situ colloidal nanocrystal surface redox chemistry. Spectroscopic measurements of the surface-bound metal carbonyl C‒O stretches were used to elucidate the coordination environments and local symmetry of surface sites. The C‒O stretching frequencies of these fragments were correlated to the electric field induced by nanocrystal surface charges and shift in energy upon surface reduction or oxidation. These measurements revealed that CdSe nanocrystals can accumulate multiple surface electrons under supra-band-gap photoexcitation, a process likely relevant to photoactivated nanocrystal processes such as photobrightening. These surface charges are stable for hours and decay extremely slowly under anaerobic conditions.

Photoinduced electrochemiluminescence (PECL) allows the electrochemically assisted conversion of low-energy photons into high-energy photons at an electrode surface. This concept is expected to have important implications, however, it is dramatically limited by the stability of the surface, impeding future developments. Here, a series of metal-insulator-semiconductor junctions, using photoactive n-type Si (n-Si) as a light absorber covered by a few-nanometer-thick protective SiO x /metal (SiO x /M, with M = Ru, Pt, and Ir) overlayers are investigated for upconversion PECL of the model co-reactant system involving the simultaneous oxidation of tris(bipyridine)ruthenium(II) and tri-n-propylamine. We show that n-Si/SiO x /Pt and n-Si/SiO x /Ir exhibit high photovoltages and record stabilities in operation (35 h for n-Si/SiO x /Ir) for the generation of intense PECL with an anti-Stokes shift of 218 nm. We also demonstrate that these surfaces can be employed for spatially localized PECL. These unprecedented performances are extremely promising for future applications of PECL.

Photoexcited structural dynamics in azo-compounds may differ fundamentally whether the push-pull photochromic azo-compound is isolated or forms a heterogeneous charge transfer complex, due to a sudden oxidation of the chromophore. Herein, we use a quantum-classical self-consistent approach that incorporates nonadiabatic excited-state electronic quantum dynamics into molecular mechanics to study the photoexcited dynamics of the push-pull azo-compound para-Methyl Red in the gas phase and sensitizing the (101) anatase surface of TiO2. We find that the photoinduced S2/S0 trans-to- cis isomerization of para-Methyl Red in the gas phase occurs through a pedal-like torsion around the ϕCNNC dihedral angle, without evidence to support the inversion mechanism, likewise in the parent azobenzene molecule. However, the photoexcited structural relaxation of the charge transfer complex para-Methyl Red/TiO2 contrasts essentially with the isolated azo-compounds. Immediately after photoexcitation, the excited electron flows into the TiO2 conduction band, with an injection time constant of ≃5 fs, and no indication of isomerization is observed during the 1.5 ps simulations. Instead, a strong vibronic relaxation occurs that excites the NN stretching mode of the azo-group, which is ultimately ascribed to the NA relaxation, and delocalization, of the hole wavepacket.

Rational design and construction of interface heterostructures, which can simultaneously accelerate the photoinduced carrier separation and enhance the surface water oxidation kinetics is of great necessity for photoelectrochemical (PEC) water oxidation. Herein, we report a new strategy for boosting the PEC water oxidation by introducing Schottky junction and semiconductor/water oxidation co-catalysts (SC/WOCs) junction into the TaON photocatalyst. Compared with pristine TaON photoanode, the hierarchical TaON/Au/ZnCo-LDH photoanode reveals a cathodic shift of 156 mV for the onset potential and 17.3-fold photocurrent density enhancement at 1.23 V vs. RHE as well as improved long-term stability. Diagnostic efficiencies of the TaON/Au/ZnCo-LDH photoanode demonstrate that the enhanced PEC performance is not dominated by surface electrochemical water oxidation kinetics but largely contributed by the improved charge separation and transfer, indicative of synergistic effects of Au and ZnCo-LDH. Theoretical calculations further reveal that the midgap states introduced by Au and ZnCo-LDH in TaON electronic structures bring about photoexcited electrons concentrated on TaON while holes accumulated on ZnCo-LDH to achieve efficiently spatial charge separation, which is responsible for the boosted PEC water oxidation performance. The present work highlights the importance and elucidates the mechanism of interface heterojunction in PEC water oxidation, which can provide an efficient approach to design and fabricate new structural photoanode.

Reduction or oxidation reactions at colloidal semiconductor nanocrystal quantum dot (QD) surfaces are critical mechanistic steps for charge trapping or for photoinduced charge transfer. However, measuring and controlling the redox potentials of the surface is nontrivial. Here, monoanionic metal carbonyl complexes are used as electronically tunable X-type ligands for CdSe and CdS QD surfaces. IR spectroscopy of the frequencies of the C-O stretching vibrations of the anionic metal carbonyl species enable quantitative measurement of anion dissociation correlated to QD surface reduction. Spectral redox titration and spectroelectrochemical experiments show that coordination of more Lewis basic anions shifts the surface reduction potentials to more negative values, spanning a range of more than 1 V. Based on these results, complexation energies are a critical factor in controlling surface charge storage. This concept extends generally to other types of QD supporting ligands and to other QD materials. As proof-of-concept, anion exchange was used to control chemical surface reduction and photochemical electronic doping in CdSe QDs.

No abstract available

No abstract available

: Gallium nitride nanowires (GaN NWs) have shown great potential in applications to photocatalysis, including photo-catalytic hydrogen evolution for solar energy storage. Previous studies have shown that GaN NWs can undergo self-improvement under light irradiation, which is attributed to surface oxidation, forming gallium oxynitride (GaON). However, the exact oxidation pathways and the effect of surface oxidation on catalytic performance remain to be understood at the molecular level. In this study, we combine computational modeling at the density functional theory (DFT) level with linear sweep voltammetry and chronoamperometric measurements to investigate the photo-induced surface oxidation of GaN NWs. We find that the oxidation of GaN to GaON is competitive with water oxidation. The oxidized surface shows almost no change in its water oxidation capabilities, although the potential required for hydrogen evolution is significantly reduced. Oxidation of the surface also leads to changes in the electronic structure, shifting the valence band edge states toward the surface adsorbed hydroxide, making hole localization there more likely. Calculations are consistent with the observation of shifts in the onset potential for photoelectrochemical hydrogen evolution toward more positive potentials over an extended 18 h period. The reported findings on the mechanism of photoinduced surface oxidation of GaN NWs and the effect of surface oxidation on hydrogen evolution provide valuable insights for the development of more efficient GaN NW-based photocatalytic surfaces for hydrogen evolution.

Controlling the surface is necessary to adjust the essential properties and desired functions of nanomaterials and devices. For nanostructured multivalent vanadium oxides, unwanted surface oxidation occurs at ambient atmosphere generally and needs to be suppressed or avoided. We describe the suppressed surface oxidation of VO2 nanostructures through blocking oxygen adsorption. During an enhanced photoinduced surface oxidation process, the increased oxidation states of vanadium in VO2 nanostructures are suppressed by the use of an inert atmosphere or coating. Intermediate oxidation states are observed, and an ALD-TiO2 coating has a good antioxidant capacity for preventing the formation of oxygen-enriched components. Such oxidation suppression is beneficial to improving the stability of VO2 nanostructures. Controllable surface oxidation helps us to understand the physical essentials of surface chemical reactions and achieve better control of surface functions and performances on correlated vanadium oxide nanostructures.

The photoinduced semiconductor-to-metal transition (PSMT) unveils crucial photodynamic mechanisms and holds great promise for information storage, sensing, optoelectronics, optical switches, etc. All previously reported PSMTs have occurred between two structural phases of the same material, lacking real-space evidence at the atomic or molecular level. Herein, we report atomic-scale observations of a photoinduced ‘face changing’: light irradiation transforms a semiconductor copper selenide (Cu2Se) surface layer on Cu(111) into a well-defined metallic Cu layer. Se atoms sink to form a new Cu2Se sublayer, while the original subsurface Cu atoms are lifted to the top layer. The Cu2Se-to-Cu transition barrier is significantly lower in the excited state compared to the ground state. Thermoactivation enables the reverse transition. The photoinduced Cu2Se-to-Cu and thermoactivated Cu-to-Cu2Se transitions are highly reversible. This work, which demonstrates PSMT between two distinct materials and photo-driven interlayer atom migration, unlocks an unconventional and intriguing route for PSMT and surface modification technologies. Photoinduced semiconductor-to-metal transitions are usually between different phases of the same material. Here the authors show the transformation of a single layer Cu2Se on Cu(111) into a metallic Cu surface layer and uncover its mechanism.

Photocatalysts with abundant oxygen vacancies (OVs) exhibit enhanced activity for the direct oxidation of benzene to phenol with O2, owing to their superior O2 activation and charge separation properties. However, OVs on metal oxide surfaces such as WO3 are susceptible to healing by oxygen-containing reactants or intermediates, leading to their irreversible deactivation. Herein, we demonstrate that incorporating Mo into the WO3 lattice effectively lowers the energy barrier for OV formation, promoting the dynamic formation of more abundant photoinduced OVs in situ on the surface during the photocatalytic reaction. These Mo-promoted photoinduced OVs are found to ensure the long-term sustainability of sufficient OVs under working conditions, enhancing photocatalytic performance and particularly its durability in the aerobic oxidation of benzene to phenol. These findings provide a straightforward strategy to overcome the issue of OV healing, enabling the sustainable operation of OV-rich photocatalysts for a range of emerging applications, even in O2-involved redox reactions.

The migration of holes in metal-oxide semiconductors such as TiO2 plays a vital role in (photo)catalytic applications. The dynamics of charge carriers under operation conditions can be influenced by both methanol addition and photoinduced surface oxygen vacancies (PI-SOVs). Nevertheless, the existing knowledge of the effect of methanol as a function of PI-SOVs solely concentrates on the chemical reduction process. For this reason, the fundamental understanding of the time-dependent charge carrier-vacancy interactions in the presence of methanol is impaired. Here, we conducted time-resolved atomic force microscopy measurements to quantitatively disclose the effect of methanol adsorption on the dynamics of hole migration in TiO2. Our results show that time constants associated with the migration of charge carriers significantly change due to methanol adsorption. Moreover, the energy landscape of the hole migration barrier was dominated and lowered by PI-SOVs. Our findings contribute to the physics of charge carrier dynamics by enabling the engineering of charge carrier-vacancy interactions.

Metal-oxide semiconductors (MOS) are widely utilized for catalytic and photocatalytic applications in which the dynamics of charged carriers (e.g., electrons, holes) play important roles. Under operation conditions, photoinduced surface oxygen vacancies (PI-SOV) can greatly impact the dynamics of charge carriers. However, current knowledge regarding the effect of PI-SOV on the dynamics of hole migration in MOS films, such as titanium dioxide, is solely based upon volume-averaged measurements and/or vacuum conditions. This limits the basic understanding of hole-vacancy interactions, as they are not capable of revealing time-resolved variations during operation. Here, we measured the effect of PI-SOV on the dynamics of hole migration using time-resolved atomic force microscopy. Our findings demonstrate that the time constant associated with hole migration is strongly affected by PI-SOV, in a reversible manner. These results will nucleate an insightful understanding of the physics of hole dynamics and thus enable emerging technologies, facilitated by engineering hole-vacancy interactions.

Adsorption of molecules is a fundamental step in all heterogeneous catalytic reactions. Nevertheless, the basic mechanism by which photon-mediated adsorption processes occur on solid surfaces is poorly understood, mainly because they involve excited catalyst states that complicate the analysis. Here we demonstrate a method by which density functional theory (DFT) can be used to quantify photoinduced adsorption processes on transition metal oxides and reveal the fundamental nature of these reactions. Specifically, the photoadsorption of SO2 on TiO2(101) has been investigated by using a combination of DFT and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The combined experimental and theoretical approach gives a detailed description of the photocatalytic desulfurization process on TiO2, in which sulfate forms as a stable surface product that is known to poison the catalytic surface. This work identifies surface-SO42– as the sulfate species responsible for the surface poisoning and shows how this product can be obtained from a stepwise oxidation of SO2 on TiO2(101). Initially, the molecule binds to a lattice O2– ion through a photomediated adsorption process and forms surface sulfite, which is subsequently oxidized into surface-SO42– by transfer of a neutral oxygen from an adsorbed O2 molecule. The work further explains how the infrared spectra associated with this oxidation product change during interactions with water and surface hydroxyl groups, which can be used as fingerprints for the surface reactions. The approach outlined here can be generalized to other photo- and electrocatalytic transition metal oxide systems.

No abstract available

In this work, we present an in situ method to probe the evolution of photoelectrochemically driven surface oxidation on photoanodes during active operation in aqueous solutions. A standard solution of K4Fe(CN)6-KPi was utilized to benchmark the photocurrent and assess progressive surface oxidation on Ta3N5 in various oxidizing solutions. In this manner, a proportional increase in the surface oxygen concentration was detected with respect to oxidation time and further correlated with a continuous decline in the photocurrent. To discern how surface oxidation alters the photocurrent, we experimentally and theoretically explored its impact on the surface carrier recombination and the interfacial hole transfer rates. Our results indicate that the sluggish photocurrent demonstrated by oxidized Ta3N5 arises because of changes in both rates. In particular, the results suggest that the N-O replacement present on the Ta3N5 surface primarily increases the carrier recombination rate near the surface and to a lesser degree reduces the interfacial hole transfer rate. More generally, this methodology is expected to further our understanding of surface oxidation atop other nonoxide semiconductor photoelectrodes and its impact on their operation.

No abstract available

Solar-assisted water splitting can potentially provide an efficient route for large-scale renewable energy conversion and storage. It is essential for such a system to provide a sufficiently high photocurrent and photovoltage to drive the water oxidation reaction. Here we demonstrate a photoanode that is capable of achieving a high photovoltage by engineering the interfacial energetics of metal–insulator–semiconductor junctions. We evaluate the importance of using two metals to decouple the functionalities for a Schottky contact and a highly efficient catalyst. We also illustrate the improvement of the photovoltage upon incidental oxidation of the metallic surface layer in KOH solution. Additionally, we analyse the role of the thin insulating layer to the pinning and depinning of Fermi level that is responsible to the resulting photovoltage. Finally, we report the advantage of using dual metal overlayers as a simple protection route for highly efficient metal–insulator–semiconductor photoanodes by showing over 200 h of operational stability. Solar water splitting using metal–insulator–semiconductor junctions has proven efficient, but these junctions degrade very rapidly. Here, the authors engineer metal–insulator–semiconductor interfaces in which Fermi-level pinning is reduced, producing an efficient and durable photoanode for solar-driven water oxidation.

The molecule water activation is believed to be one of the most critical steps that is closely related to the proceeding of photoinduced reaction, such as overall water splitting, carbon dioxide conversion, and organic contaminant degradation. As metal oxides possessing a regular structure with high crystallinity are widely accepted as promising for effective catalysis, numerous studies have been devoted to the relevant photoinduced applications. However, their irregular derivative phases with lower crystallinity, which could exhibit tempting opportunities for catalytic activities, have long been ignored. Here, the surface-amorphized bismuth oxychloride is produced by homogeneous nanoparticle distribution through a rapid precipitation strategy. Comparing with its surface-crystallized counterpart, the partially amorphized bismuth oxychloride undergoes a fast surface reconstruction process under light irradiation, forming active surfaces with rich oxygen vacancies (OVs), leading to not only distinctive OV-mediated interfacial charge-transfer mechanisms with improved carrier dynamics but also robust water-surface interface with enhanced physical and chemical interaction, thus resulting in enhanced photocatalytic water oxidation. The strategy of optimizing by tuning the interfacial interaction behavior proposed in this work could broaden horizons for establishing more efficient partially amorphized energy conversion materials.

A limiting factor to the efficiency of water Oxygen Evolution Reaction (OER) in metal oxide nanoparticle photocatalysts is the rapid recombination of holes and electrons. Facet-engineering can effectively improve charge separation and, consequently, OER efficiency. However, the kinetics behind this improvement remain poorly understood. This study utilizes photoinduced absorption spectroscopy to investigate the charge yield and kinetics in facet-engineered BiVO4 (F-BiVO4) compared to a non-faceted sample (NF-BiVO4) under operando conditions. A significant influence of preillumination on hole accumulation is observed, linked to the saturation and, thus, passivation of deep and inactive hole traps on the BiVO4 surface. In DI-water, F-BiVO4 shows a 10-fold increase in charge accumulation (∼5 mΔOD) compared to NF-BiVO4 (∼0.5 mΔOD), indicating improved charge separation and stabilization. With the addition of Fe(NO3)3, an efficient electron acceptor, F-BiVO4 demonstrates a 30-fold increase in the accumulation of long-lived holes (∼45 mΔOD), compared to NF-BiVO4 (∼1.5 mΔOD) and an increased half-time, from 2 to 10 s. Based on a simple kinetic model, this increase in hole accumulation suggests that facet-engineering causes at least a 50–100 meV increase in band bending in BiVO4 particles, thereby stabilizing surface holes. This energetic stabilization/loss results in a retardation of OER relative to NF-BiVO4. This slower catalysis is, however, offset by the observed increase in density and lifetime of photoaccumulated holes. Overall, this work quantifies how surface faceting can impact the kinetics of long-lived charge accumulation on metal oxide photocatalysts, highlighting the trade-off between lifetime gain and energetic loss critical to optimizing photocatalytic efficiency.

Colloidal semiconductor quantum dots (QDs) are promising candidates for various applications in electronics and quantum optics. However, they are sensitive and vulnerable to the chemical environment due to their highly dynamic surface with a large portion of exposed atoms. Hence, oxidation and detrimental defects on the nanocrystal (NC) interface dramatically deteriorate their optical as well as electrical properties. In this study, a simple strategy is proposed not only to obtain good preservation of colloidal semiconductor QDs by using a protective polymer matrix but also to provide excellent accessibility to micro-fabrication by optical lithography. A high-quality QD–polymer nanocomposite with mono-dispersion of the NCs is synthesized by incorporating the colloidal CdSe/CdS NCs into an SU-8 photoresist. Our approach shows that the oxidation of the core/shell QDs embedded in the SU-8 resist is completely avoidable. The deterministic insertion of multiple QDs or a single QD into photonic structures is demonstrated. Single photon generation is obtained and well-preserved in the nanocomposite and the polymeric structures.

Photostability of semiconductor core/shell quantum dots (QDs) has historically been perceived as intricate and unpredictable. Notably, the long-term luminescence stability of QDs under light exposure does not seem to consistently correspond with their characteristics in the absence of light. In this study, we propose a positive photoaging mechanism of QDs, integrating both ligand/shell-induced photobrightening and surface photo-oxidation, to deal with the photostability nuances. When QDs are subjected to higher energy light, their photobrightening and photodarkening conjointly determine the photostability. Enhanced photostability may not be simply attributed to a thicker shell or the presence of ligands. When adjusted with an optimal shell thickness and supplemented with negatively charged ligands, QDs exhibit enhanced photostability in both solvents and polymers.

Currently, the further performance improvement for inverted perovskite solar cells (PVSCs) is mainly limited by the high open circuit voltage ( V OC ) loss caused by the detrimental non-radiative recombination (NRR) processes. Herein, we report a simple and efficient way to simultaneously reduce the NRR processes inside perovskite and at the interface by rationally designing a new pyridine-based polymer hole transporting material (HTM), i. e. PPY2 , which exhibits suitable energy levels with perovskites, high hole mobility, effective passivation of the uncoordinated Pb 2+ and iodide defects, as well as the capability of promoting the formation of high quality polycrystalline perovskite film. In absence of any dopants, the inverted PVSCs using PPY2 as the HTM deliver an encouraging PCE up to 22.41% with a small V OC loss (0.40 eV), among the best device performance for inverted PVSCs reported so far. Furthermore, PPY2 -based unencapsulated devices show an excellent long-term photostability, and over 97% of its initial PCE can be maintained after one sun constant illumination for 500 h.

No abstract available

Quantum dots (QDs) are inorganic semiconductor nanocrystals capable of emitting light. The current major challenge lies in the use of heavy metals, which are known to be highly toxic to humans and pose significant environmental risks. Researchers have turned to indium (In) as a promising option for more environmentally benign QDs, specifically indium phosphide (InP). A significant obstacle remains in sustaining the long-term photostability of InP-based QDs when exposed to the environment. To tackle this, electrospraying is used in this work to protect indium phosphide/zinc selenide/zinc sulfide (InP/ZnSe/ZnS) QDs by embedding them within polymer core-shell microparticles of poly[(lauryl methacrylate)-co-(ethylene glycol dimethacrylate)]/poly(methyl methacrylate) (poly(LMA-co-EGDMA)/PMMA). During the flight of droplets, the liquid monomer core of LMA and EGDMA with QDs is encapsulated by the solid shell of PMMA formed due to solvent evaporation, resulting in a liquid-core/solid-shell particle structure. After that, the captured core of monomers is polymerized into a cross-linked polymer with the embedded QDs via a thermal initiation. They demonstrate how a successful core-shell particle formation is achieved to produce structures for initially liquid monomer systems via coaxial electrospraying that are used for cross-linked polymers, which are of major interest for the encapsulation of InP-based QDs for generally improved photostability over pristine QDs.

Förster (or fluorescence) resonance energy transfer amongst semiconductor quantum dots (QDs) is reviewed, with particular interest in biosensing applications. The unique optical properties of QDs provide certain advantages and also specific challenges with regards to sensor design, compared to other FRET systems. The brightness and photostability of QDs make them attractive for highly sensitive sensing and long-term, repetitive imaging applications, respectively, but the overlapping donor and acceptor excitation signals that arise when QDs serve as both the donor and acceptor lead to high background signals from direct excitation of the acceptor. The fundamentals of FRET within a nominally homogeneous QD population as well as energy transfer between two distinct colors of QDs are discussed. Examples of successful sensors are highlighted, as is cascading FRET, which can be used for solar harvesting.

Silicon carbide (SiC) hosts a number of point defects that are being explored as single-photon emitters for quantum applications. Unfortunately, these quantum emitters lose their photostability when placed in the proximity of the surface of the host semiconductor. In principle, a uniform passivation of the surface’s dangling bonds by simple adsorbates, such as hydrogen or mixed hydrogen/hydroxyl groups, should remove detrimental surface effects. However, the usefulness of atomic and molecular passivation schemes is limited by their lack of long-term chemical and/or thermal stability. In this first-principles work, we use aluminum nitride (AlN) to passivate SiC surfaces in a core–shell nanowire model. By using a negatively charged silicon vacancy in SiC as the proof-of-principle quantum emitter, we show that AlN-passivation is effective in removing SiC surface states from the bandgap and in restoring the defect’s optical properties. We also report the existence of a silicon vacancy-based defect at the SiC–AlN interface, which displays distinct spin and optical properties as compared to the other well-studied defects in SiC.

No abstract available

No abstract available

Nickel oxide (NiOx), a typical p-type semiconductor, is emerging as the most promising hole transport layer material. However, the inferior interfacial contact of the NiOx/perovskite interface has limited the improvement of the performance of photodetectors (PDs). In this work, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) is introduced to modify the NiOx/perovskite interface to prepare high-performance PDs. This study shows that the F4-TCNQ layer interacts with the NiOx/perovskite layers. It can increase the Ni3+/Ni2+ ratio and then enhance the hole extraction and charge carrier mobility; on the contrary, it can form a new Lewis adduct and passivate the undercoordinated Pb2+ ions. Furthermore, with the F4-TCNQ modification, the perovskite film exhibits good thermal stability and photostability. The PDs demonstrate excellent photoelectric properties and long-term stability in the atmosphere. This finding provides a simple and efficient way to further develop the NiOx/perovskite interface.

No abstract available

No abstract available

Semiconductor quantum dots (QDs) have demonstrated utility in long-term single particle tracking of membrane proteins in live cells in culture. To extend the superior optical properties of QDs to more physiologically relevant cell platforms, such as acute brain slices, we examine the photophysics of compact ligand-conjugated CdSe/CdS QDs using both ensemble and single particle analysis in brain tissue media. We find that symmetric core passivation is critical for both photostability in oxygenated media and for prolonged single particle imaging in brain slices. We then demonstrate the utility of these QDs by imaging single dopamine transporters in acute brain slices, achieving 20 nm localization precision at 10 Hz frame rates. These findings detail design requirements needed for new QD probes in complex living environments, and open the door to physiologically relevant studies that capture the utility of QD probes in acute brain slices.

No abstract available

Large‐scale bismuth vanadate (BiVO4) photoanodes are critical to the practical application of photoelectrochemical water splitting devices. However, the lack of interface‐modified coatings with simultaneous low cost, scalability, high hole transport efficiency, low impedance, and photocorrosion resistance is a major challenge that prevents the practical application of large‐size photoanodes. Here, we present a scalable nickel‐chelated polydopamine conformal coating for modifying BiVO4 (BiVO4@PDA‐Ni, BPNi), achieving over 500 h of stable water oxidation at 0.6 VRHE. The excellent stability is attributed to the chelated Ni acting as hole oxidation sites for PDA, thereby suppressing the accumulated‐holes‐induced PDA decomposition. Additionally, the in situ generation of Ni(IV) facilitates the structural reorganization of PDA in the photoelectrochemical system, further enhancing the stability of the PDA matrix. The findings of PDA photodegradation, its autonomous metal ion capture within photoelectrochemical systems, and the rapid deactivation of BPNi photoanodes caused by vanadium (V) ions have all provided significant guidance for the enhancement of PDA. Our study demonstrates that nickel‐chelated polydopamine can be applied to large‐scale BiVO4 photoanodes to facilitate oxygen evolution. This will promote the development of large‐scale photoanodes suitable for photoelectrochemical devices.

Increasing long-term photostability of BiVO 4 photoanode is an important issue for solar water splitting, NiOOH oxygen evolution catalyst (OEC) has a fast water oxidation kinetics compared to FeOOH OEC.  However, it generally shows a relatively lower photoresponse and poor stability compared to FeOOH due to the more substantial interface recombination at the NiOOH/ BiVO 4 junction. In this work, we utilize a feasible plasma etching approach to reduce both interface/surface recombination at NiOOH/ BiVO 4 and NiOOH/electrolyte junctions. Further, adding Fe 2+ into the borate buffer electrolyte alleviates the active but unstable character of etched-NiOOH/BiVO 4 , leading to an outstanding oxygen evolution over 200 h. The improved charge transfer and photostability can be attributed to the active defects and a mixture of NiOOH/NiO/Ni in OEC induced by plasma etching treatment. Metallic Ni acts as the ion source for the in-situ generation of the NiFe OEC over long-term durability.

Prolonged (weeks) UV-Vis irradiation under Ar of UiO-66(Zr), UiO66 Zr-NO 2 , MIL101 Fe, MIL125 Ti-NH 2 , MIL101 Cr and MIL101 Cr(Pt) shows that these MOFs undergo photodecarboxylation of benzenedicarboxylate (BDC) linker in a significant percentage depending on the structure and composition of the material. Routine characterization techniques such as XRD, UV-Vis spectroscopy and TGA fail to detect changes in the material, although porosity and surface area change upon irradiation of powders. In contrast to BCD containing MOFs, zeolitic imidazolate ZIF-8 does not evolve CO 2 or any other gas upon irradiation.

No abstract available

The benzodithiophene‐based donor polymer PM6 is widely used in organic solar cells (OSCs), but its practical application is hindered by poor photostability, mainly due to structural twisting and photo‐oxidation under prolonged light exposure. To address this limitation, a crosslinkable donor polymer, PM6‐Br is designed and synthesized to investigate the effect of crosslinking on photostability. Although PM6‐Br exhibits optical and photoelectrical properties comparable to those of PM6, its crosslinked form showed significantly improved resistance to photo‐oxidation and enhanced morphological stability under continuous irradiation. X‐ray photoelectron spectroscopy (XPS), resonance Raman spectroscopy and time‐dependent density functional theory (TD‐DFT) analyses reveal that PM6 undergoes substantial photo‐oxidation—specifically sulfur oxidation—resulting in energy level shifts, the formation of trap states, and molecular aggregation. Raman signals associated with the conjugated backbone decrease more rapidly in PM6 than in PM6‐Br, indicating more extensive structural degradation. The enhanced photostability of the crosslinked donor polymer led to improve device stability, with OSCs based on crosslinked PM6‐Br maintaining significantly better operational performance under continuous 1‐sun irradiation for 1000 h. These findings highlight crosslinking as a promising strategy to improve the photostability of OSCs, advancing their potential for commercial applications.

The use of novel two-dimensional MXene materials and conventional g-C3N4 photocatalysts to fabricate the composites for hydrogen evolution reaction (HER) has attracted much attention, for which there is plenty of room for the enhancement of hydrogen evolution rates particularly under visible light and photostability. Herein, g-C3N4 was modified by copolymerization of malonamide and melamine and used to fabricate the ternary composites of Au particles and Ti3C2 MXene, and based on the synergistic effect, the composites enhanced the hydrogen evolution rates by 2.1, 99.8, and ∞ times compared with the unmodified g-C3N4 under UV, simulated sunlight, and visible light illumination, respectively. Moreover, the composite exhibited a sustained hydrogen evolution capacity in the cycle test for up to 120 h. Theoretical calculations and experimental results indicated that the hot electrons of Au are injected into the modified g-C3N4 and transferred to Ti3C2 simultaneously along with the photogenerated electrons of the modified g-C3N4 and then further transferred to Au, forming a photogenerated electron transfer channel of Au and modified g-C3N4 → Ti3C2 → Au within the composite. Ti3C2 acts as a bridge for fast separation of photogenerated electrons and holes on Au and modified g-C3N4, playing a key role in the enhanced photocatalytic performance. In addition, the visible light absorption ability of Au also positively contributed to the enhancement of visible light photocatalytic performance by providing hot electrons. Therefore, the selection of suitable cocatalysts for the design of composites is a crucial research direction to improve the photocatalytic performance and photostability of photocatalysts.