Reverse Water Gas Shift Reaction

The reverse water-gas shift reaction (RWGSR), a crucial stage in the conversion of abundant CO2 into chemicals or hydrocarbon fuels, has attracted extensive attention as a renewable system to synthesize fuels by non-traditional routes. There have been persistent efforts to synthesize catalysts for industrial applications, with attention given to the catalytic activity, CO selectivity, and thermal stability. In this review, we describe the thermodynamics, kinetics, and atomic-level mechanisms of the RWGSR in relation to efficient RWGSR catalysts consisting of supported catalysts and oxide catalysts. In addition, we rationally classify, summarize, and analyze the effects of physicochemical properties, such as the morphologies, compositions, promoting abilities, and presence of strong metal-support interactions (SMSI), on the catalytic performance and CO selectivity in the RWGSR over supported catalysts. Regarding oxide catalysts (i.e., pure oxides, spinel, solid solution, and perovskite-type oxides), we emphasize the relationships among their surface structure, oxygen storage capacity (OSC), and catalytic performance in the RWGSR. Furthermore, the abilities of perovskite-type oxides to enhance the RWGSR with chemical looping cycles (RWGSR-CL) are systematically illustrated. These systematic introductions shed light on development of catalysts with high performance in RWGSR.

… The reverse water gas shift (RWGS) reaction is a promising technology for introducing carbon dioxide as feedstock to the broader chemical industry through syngas production. While …

… rate of reaction of the homogeneous, reverse water–gas shift … of the forward and reverse reaction rates would be useful in … The reverse water–gas shift reaction (rWGSR) is the focus of …

… The reverse water gas shift reaction (RWGS) and the reaction with CO2 alone were carried out over a Cu/ZnO catalyst. The surface of the catalyst was characterized by N20 titration, XPS…

… Catalytic reverse water gas shift (RWGS) reaction has been regarded as an attractive route for the conversion of waste CO 2 to valuable CO. Despite Pt being facile for hydrogenation, …

… Catalytic reverse water gas shift reaction was conducted in an electric field (denoted as E-RWGS) over various catalysts at low temperature as 423 K. A platinum catalyst supported on …

The catalytic conversion of CO2 to CO via a reverse water gas shift (RWGS) reaction followed by well-established synthesis gas conversion technologies may provide a potential approach to convert CO2 to valuable chemicals and fuels. However, this reaction is mildly endothermic and competed by a strongly exothermic CO2 methanation reaction at low temperatures. Therefore, the improvement in the low-temperature activities and selectivity of the RWGS reaction is a key challenge for catalyst designs. We reviewed recent advances in the design strategies of supported metal catalysts for enhancing the activity of CO2 conversion and its selectivity to CO. These strategies include varying support, tuning metal–support interactions, adding reducible transition metal oxide promoters, forming bimetallic alloys, adding alkali metals, and enveloping metal particles. These advances suggest that enhancing CO2 adsorption and facilitating CO desorption are key factors to enhance CO2 conversion and CO selectivity. This short review may provide insights into future RWGS catalyst designs and optimization.

The reverse water gas shift (RWGS) reaction converts carbon dioxide (CO2) and hydrogen (H2) to syngas, which is used to produce various high-added-value chemicals. This process has attracted great interest from researchers as a way of mitigating the potential environmental impacts of this greenhouse gas, with emphasis on global warming. This work aims to model and simulate an industrial catalytic reactor using kinetic data for the RWGS reaction. The simulation was carried out in Aspen Plus® v10. The thermodynamic analysis showed that the appropriate conditions for the reaction are feed molar ratio (H2/CO2) of 0.8:1, 750 °C, and 20 bar. The RWGS process proceeds in a multi-tubular fixed bed reactor with 36.26% CO2 conversion and 96.41% CO selectivity, at residence times in the order of 2.7 s. These results are at near-equilibrium CO2 conversion with higher CO selectivity.

A reactant-promoted reaction mechanism for reverse water-gas shift reaction (H 2 + CO 2 → H 2 O + CO; r-WGSR) on ZnO was investigated by FT-IR, MS, and GC. Surface bidentate …

… for the forward water gas shift reaction because the nature of the surface of the catalyst will depend on the composition of the reaction mixture. This will be the subject of future work. …

… [1] indicate that in operando studies are necessary in order to provide true insight into reaction mechanisms, such as the reverse water-gas shift (RWGS) reaction over metal/ceria …

… to CO by reverse water gas shift reaction followed by CO conversion to fuels with FTS had the highest current and estimated potential efficiency when CO 2 is captured from a flue gas or …

… In this study, the selectivity of the reverse water–gas-shift reaction using Pt/TiO 2 catalysts was examined. The optimum calcination temperature was determined to be 923 K with regard …

… in proton exchange membrane fuel cells (PEMFCs), and recent evidence has shown that CO 2 can react in situ with H 2 (ie, a reverse water gas shift (RWGS) reaction) and produce …

Abstract The reverse water–gas shift reaction (RWGSR) using a supported ionic liquid-phase (SILP) catalyst consisting of Ru catalyst, ionic liquid (1-butyl-3-methylimidazolium chloride ([C4mim]Cl)), and porous silica gel support, was investigated. The catalytic activity of the SILP catalyst toward RWGSR strongly depends on the kind of Ru catalyst and amount of IL. Among the three kinds of Ru catalysts ([RuCl2(CO)3]2, Ru3(CO)12, and RuCl3), [RuCl2(CO)3]2 exhibits the best catalytic activity. Brunauer–Emmett–Teller (BET) surface area analysis and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses of the SILP catalyst based on [RuCl2(CO)3]2 and [C4mim]Cl revealed that both the solvation of the active catalytic Ru species and the surface area of the ionic liquid phase strongly affect catalytic activity. Hence, these factors help to determine the optimum amount of [C4mim]Cl in the SILP catalyst. The resulting SILP catalyst, with an optimum constitution, exhibited greater catalytic activity than the homogeneous system in which the same amounts of [RuCl2(CO)3]2 and [C4mim]Cl were employed. Catalytically active Ru species during RWGSR in both systems were investigated by means of electrospray ionization-mass spectrometry (ESI-MS). Interestingly, the rate-determining step in the two systems was different, implying that the silica support lowers the activation energy of the protonation reaction in the catalytic cycle. Therefore, the facilitation of the RWGSR by a SILP catalyst system can be realized by good mass transport, derived from the large surface area, as well as the effect of the silica support on activation energy. Furthermore, 20 cycles of the RWGSR using the SILP catalyst were accomplished.

… Reverse water gas shift (RWGS) reaction can serve as a pivotal stage in the CO 2 conversion processes, which is vital for the utilization of CO 2 . In this study, RWGS reaction was …

… We show that localized surface plasmon resonance (LSPR) can enhance the catalytic activities of different oxide-supported Au catalysts for the reverse water gas shift (RWGS) reaction. …

CO2 conversion and reuse technology are crucial for alleviating environmental stress and promoting carbon cycling. Reverse water gas shift (RWGS) reaction can transform inert CO2 into active CO. Molybdenum carbide (MoC) has shown good performance in the RWGS reaction, and different crystalline phases exhibit distinct catalytic behaviors. Here, we performed a systematic study on the RWGS reaction mechanism on the hexagonal-phase γ-MoC(100) surface by using density functional theory (DFT). It is found that the redox mechanism, i.e. the direct dissociation of CO2, is the dominant pathway. CO2 firstly adsorbs on the surface with an adsorption energy of −2.14 eV, and then dissociates into CO* and O* with a barrier of 0.83 eV. Surface O* hydrogenating into OH* has a high barrier of 2.15 eV. OH* further hydrogenating into H2O* has a barrier of 1.48 eV, and the disproportionation of OH* considerably lowers this value to 0.06 eV. However, the desorption of product CO is particularly challenging due to the large energy demand of 3.06 eV. This characteristic, in turn, provides feasibility and opportunity for CO2 to serve as a potential alternative carbon source for CO on the γ-MoC(100) surface. In contrast, other Mo-based catalysts such as hexagonal MoP and cubic α-MoC have better RWGS catalytic efficiency.

With the continuous increase in CO2 emissions, primarily from the combustion of coal and oil, the ecosystem faces a significant threat. Therefore, as an effective method to minimize the issue, Reverse Water Gas Shift (RWGS) reaction which converts CO2 towards CO attracts much attention, is an environmentally-friendly method to mitigate climate change and lessen dependence on fossil fuels. Nevertheless, the inherent thermodynamic stability and kinetic inertness of CO2 is a big challenge under mild conditions. In addition, it remains another fundamental challenge in RWGS reaction owing to CO selectivity issue caused by CO2 further hydrogenation towards CH4. Up till now, a series of catalysis systems have been developed for CO2 and H2 reduction reaction to produce CO. Herein, the research progress of the well-performed heterogeneous catalysts for the RWGS reaction were summarized, including the catalyst design, catalytic performance and reaction mechanism. This review will provide insight into efficient utilization of CO2 and will promote the development of RWGS reaction.

… CO 2 levels and curtailing our reliance on fossil fuels. Notably, the hydrogenation of CO 2 to CO via the reverse water–gas shift (… during CO 2 hydrogenation. Consequently, studies on …

… that the CO 2 hydrogenation … CO 2 hydrogenation reaction occurs via intermediate formation of adsorbed CO species (Ru x -CO, Ru n+ (CO) x , (TiO 2 )Ru-CO) produced via the RWGS …

… Intensifying CO 2 hydrogenation reactions by in-… ) reverse water–gas shift (RWGS) reaction was explored as a case study since it represents the starting point of all CO 2 hydrogenation …

… ethanol during CO hydrogenation, they functioned primarily as methanation catalysts during CO 2 hydrogenation. The Fe/TiO 2 sample was primarily a reverse water gas shift catalyst. …

The conversion of CO2 into chemical fuels represents an attractive route for greenhouse gas emission reductions and renewable energy storage. Iron nanoparticles supported on graphitic carbon materi...

… The reverse water gas shift (RWGS) reaction over Cu/SiO 2 with and without potassium promoter was studied by means of CO 2 hydrogenation, temperature programmed reduction (…

… of thermo-catalytic CO 2 hydrogenation selectivity by the … We first introduce the reaction mechanism of CO 2 hydrogenation … the reverse water–gas shift (RWGS, CO 2 hydrogenation to …

… rates of methanol synthesis and RWGS are both inhibited by … precluding sequential RWGS and CO hydrogenation as the … forward and reverse rates of CO 2 hydrogenation on Cu/ZnO/Al …

… , the conversion of CO 2 by RWGS is limited at … /CO 2 ratio of 3 (stoichiometric ratio for CO 2 hydrogenation to CH 2 ) at temperatures between 220 and 300 C, only 13–23 % of CO 2 …

Abstract The direct conversion of carbon dioxide to hydrocarbons is one of the key solutions to both the reduction of the greenhouse effect and the sustainable production of fuels and lubricants. Here, it is demonstrated that simple bimetallic Ru/Ni nanoparticles (NPs) (2–3 nm, Ru-rich shell, and Ni-rich core) in a hydrophobic ionic liquid (IL) promote the direct hydrogenation of CO2 to light hydrocarbons (HCs) under very mild reaction conditions in a simple batch reactor. The reaction of CO2 with hydrogen (1:4, 8.5 bar) at 150 °C with the Ru/Ni NPs (3:2) in bis((trifluoromethyl)sulfonyl)amide (BMI.NTf2) hydrophobic IL affords C2+ hydrocarbons (79% alkanes and 16% olefins) with 5% CH4 at 30% conversion. However, the reaction performed in the hydrophilic IL 1-n-butyl-3-methyl-1H-imidazol-3-ium tetrafluoroborate affords mainly CO. The catalytic hydrogenation of CO2 towards HCs proceeds by a two-step process with the initial conversion of CO2 into CO by reverse gas shift reaction (RWGS), followed by Fischer-Tropsch Synthesis (FTS). The bimetallic NPs have higher catalytic efficiencies than their monometallic counter- parts, owing to strong synergy between the metals. The presence of Ni in the bimetallic NPs yields a more active RWGS catalyst, and the Ru increases the FTS towards heavier HCs.

… progress in mechanistic studies of CO 2 hydrogenation to C1 (CO, CH … the selective conversion of CO 2 on metal/oxide catalysts. … CO 2 hydrogenation to CO via the RWGS reaction, can …

… *H 2 CO and the *HCOO hydrogenation to *HCOOH along the … by the CO 2 hydrogenation to *HOCO along the RWGS + CO-… catalysts during CO 2 hydrogenation along the RWGS + CO-…

… hydrogenation of CO 2 . The major product over these catalysts is CO which is produced by the reverse water–gas shift reaction (RWGS, CO 2 … of CO through the RWGS, with the …

… consecutive RWGS and FTS reactions, also known as CO 2 … RWGS and FTS. In this work, we investigated the thermodynamic constraints of RWGS and CO 2 -FTS, the influence of CO 2 …

… A hydroxyl (on ZnO)-promoted RWGS reaction cycle is … Our results provide a way to regulate RWGS reaction on Cu/… CO and CO 2 via RWGS/WGS reaction on hydrogenation catalysts. …

Abstract The metal-support interfaces of metallic nanoparticles supported on oxide surfaces determine the activated dissociation of CO 2 in CO 2 hydrogenation. It also guides the catalytic pathway towards either CO 2 methanation or reverse water-gas shift (rWGS). In this work, Ru/Al 2 O 3 catalysts with different Ru structural configurations were prepared by controlling the Ru weight loadings, which revealed the structure-dependence of production rates for CO and CH 4 formation with different apparent activation energies. Based on the characterization results, two catalyst models were setup: the Ru 9 /Al 2 O 3 model consisted of an interface of monolayer Ru sites tightly contacted with γ -Al 2 O 3 support, and the Ru 35 /Al 2 O 3 model represented a relatively larger Ru nanocluster supported on γ -Al 2 O 3 . Theoretical calculations of these two models demonstrated that monolayer Ru sites favored the rWGS route with a relatively low energy barrier for both CO 2 activation and CO formation steps, while Ru nanoclusters preferred the methanation route energetically. Furthermore, the combination of theoretical calculations and experimental isotope-exchange measurements suggested that the interfacial O species in Ru-O-Al interfaces played a critical role in CO 2 activation via oxygen-exchanging with the O atom in the feeding CO 2 and consequently incorporation into the final hydrogenation product.

A combination of time-resolved X-ray diffraction (TR-XRD), ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), and diffuse reflectance infrared Fourier transform spectroscopy was used to carry out in situ characterization of Cu/CeO2 nanocatalysts during the hydrogenation of CO2. Morphological effects of the ceria supports on the catalytic performances were investigated by examining the behavior of copper/ceria nanorods (NR) and nanospheres. At atmospheric pressures, the hydrogenation of CO2 on the copper/ceria catalysts produced mainly CO through the reverse water–gas shift (RWGS) reaction and a negligible amount of methanol. The Cu/CeO2-NR catalyst displayed the higher activity, which demonstrates that the RWGS is a structure-sensitive reaction. In situ TR-XRD and AP-XPS characterization showed significant changes in the chemical state of the catalysts under reaction conditions, with the copper being fully reduced and a partial Ce4+ → Ce3+ transformation occurring. A more effective CO2 dissociati...

Summary Harnessing solar power to convert carbon dioxide (CO2) into fuels is a crucial channel to alleviate the global energy shortage and environment pollution. Photothermal catalytic conversion of CO2 into value-added fuels or chemicals, e.g., carbon monoxide (CO), methane (CH4), and methanol (CH3OH), offers an effective, economical, and eco-friendly solution to obtain “sunshine” feedstocks by coupling renewable solar energy with heat energy. In this review, we begin by briefly describing the fundamentals for photothermal catalytic CO2 reduction. Subsequently, we summarize the types of nanocatalysts for photothermal catalysis and their design strategies, where we propose two major photothermal catalytic mechanisms based on semiconductors and plasmonic metals, followed by three key design strategies of nanomaterials for photothermal catalytic CO2 reduction. Then, we expatiate the recent typical applications of photothermal catalytic CO2 reduction. Finally, we present our vision of the future developments and challenges in this exciting research field.

MXenes, a novel family of 2D materials, are energy materials that have gained considerable attention, particularly for their catalytic applications in emerging areas such as CO2 and N2 hydrogenation. Herein, for the first time, it is shown that the surface reducibility of Ti3 C2 Tx MXene can be tuned by N doping, which induces a change in the catalytic properties of supported Co nanoparticles. Pristine Co-Ti3 C2 Tx MXene favors CO production during CO2 hydrogenation, whereas CH4 production is favored when the MXene is subjected to simple N doping. X-ray photoelectron spectroscopy and transmission electron microscopy (TEM) reveal that surface rutile TiO2 nanoparticles appear on the Ti3 C2 Tx support upon N doping, which interact strongly with the supported Co nanoparticles. This interaction alters the reducibility of the supported Co nanoparticles at the interface with the TiO2 nanoparticles, shifting the product selectivity from CO to CH4 . This study successfully showcases a practical strategy, based on surface chemistry modulation of 2D MXenes, for regulating product distribution in CO2 hydrogenation.

… reducing CO 2 emissions while fossil fuels continue to dominate the energy sector. Reducing CO 2 by H 2 using heterogeneous catalysis … selective and stable catalysts suitable for large-…

… and the easy separation of products from catalysts. Research has proved that photocatalysis… able to reduce CO 2 to produce a variety of organic compounds such as carbon monoxide, …

Continuous consumption of fossil energy and excessive CO2 emission severely restrict human society. Sustainable carbon cycle is a promising technology to simultaneously relieve greenhouse effect and energy crisis based on electrocatalysis and photocatalysis. However, the energy conversion efficiency is confined by the poor carriers utilization and insufficient reactive sites. Single‐atom catalysts (SACs) display outstanding performance in effectively overcoming the aforementioned problems. Herein, recent advances of SACs for enhancing the efficiency, selectivity, and long‐range stability of CO2 reduction are provided. First, the characteristics of SACs have been introduced in detail to provide rational design for SACs based on the relationship between structure and performance, including type, structure, and synthesis of SACs. Then, the high performance of SACs in electrocatalytic, photocatalytic, and thermocatalytic CO2 reduction has been discussed for disclosing reaction mechanism, such as charge transfer, activation barriers, and reaction pathway. In particular, the strategies of enhancing CO2 reduction performance have been summarized to provide deep insight into designing and developing more efficient SACs. Finally, an outlook on the current challenges and perspectives of SACs for electrocatalytic, photocatalytic, and thermocatalytic CO2 reduction is proposed. This review aims to provide a systematic reference for developing SACs in advanced CO2 catalytic conversion.

… The mechanism of the reverse water–gas shift reaction over a Cu catalyst was studied by … the RWGS reaction in more detail. The mechanism of the RWGS reaction was studied on a …

… simulations, we have investigated the mechanisms of rWGS reaction on Ru adsorption on a … mechanisms involve both direct dissociation mechanisms and an associative mechanism. …

The catalytic conversion of CO2 to CO by the reverse water gas shift (RWGS) reaction followed by well-established synthesis gas conversion technologies could be a practical technique to convert CO2 to valuable chemicals and fuels in industrial settings. For catalyst developers, prevention of side reactions like methanation, low-temperature activity, and selectivity enhancements for the RWGS reaction are crucial concerns. Cerium oxide (ceria, CeO2) has received considerable attention in recent years due to its exceptional physical and chemical properties. This study reviews the use of ceria-supported active metal catalysts in RWGS reaction along with discussing some basic and fundamental features of ceria. The RWGS reaction mechanism, reaction kinetics on supported catalysts, as well as the importance of oxygen vacancies are also explored. Besides, recent advances in CeO2 supported metal catalyst design strategies for increasing CO2 conversion activity and selectivity towards CO are systematically identified, summarized, and assessed to understand the impacts of physicochemical parameters on catalytic performance such as morphologies, nanosize effects, compositions, promotional abilities, metal-support interactions (MSI) and the role of selected synthesis procedures for forming distinct structural morphologies. This brief review may help with future RWGS catalyst design and optimization.

High-temperature chemical reactions are ubiquitous in (electro) chemical applications designed to meet the growing demands of environmental and energy protection. However, the fundamental understanding and optimization of such reactions are great challenges because they are hampered by the spontaneous, dynamic, and high-temperature conditions. Here, we investigated the roles of metal catalysts (Pd, Ni, Cu, and Ag) in the high-temperature reverse water-gas shift (RWGS) reaction using in-situ surface analyses and density functional theory (DFT) calculations. Catalysts were prepared by the deposition-precipitation method with urea hydrolysis and freeze-drying. Most metals show a maximum catalytic activity during the RWGS reaction (reaching the thermodynamic conversion limit) with formate groups as an intermediate adsorbed species, while Ag metal has limited activity with the carbonate species on its surface. According to DFT calculations, such carbonate groups result from the suppressed dissociation and adsorption of hydrogen on the Ag surface, which is in good agreement with the experimental RWGS results.

Abstract The reverse water‐gas shift (RWGS) reaction offers a promising pathway for CO₂ utilization by converting CO₂ and H₂ into CO and H 2 O. This review explores the thermodynamic challenges of the RWGS process, emphasizing the need for high temperatures to suppress side reactions such as methane and coke formation. For catalytic RWGS reaction, reaction mechanism and catalytic materials are discussed together with kinetic models to provide an insight into RWGS performance under varying conditions. Catalyst deactivation mechanisms, particularly metal sintering and coke deposition, are addressed, with strategies for enhancing catalyst longevity through material optimization. RWGS applications are discussed, demonstrating the potential for integrating RWGS into industrial settings.

Reverse water–gas shift (RWGS) reaction has attracted much attention as a potential approach for CO2 valorization via the production of synthesis gas, especially over Fe-modified supported Cu catalysts on CeO2. However, most studies have focused solely on investigating the RWGS reaction over catalysts with high Cu and Fe loadings, thus leading to an increase in the complexity of the catalytic system and, hence, preventing the gain of any reliable information about the nature of the active sites and reaction mechanism. In this work, a CeO2-supported single-atom Cu catalyst modified with iron was synthesized and evaluated for the RWGS reaction. The catalytic results reveal a significant synergistic effect between CuCeO2 and Fe, demonstrating an activity up to three times higher than the combined catalytic activities of monometallic catalysts (Fe/CeO2 + CuCeO2) under identical conditions. Various ex situ and in situ/operando techniques are employed to unveil the concealed role of Fe in catalyst activity enhancement. The combined findings from hydrogen temperature-programmed reduction (H2-TPR) and operando electron paramagnetic resonance spectroscopy (EPR) reveal that the added Fe predominantly interacts with Cu-containing surface sites, resulting in the stabilization of higher proportions of Cu single sites. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and operando EPR results unveil a synergistic interplay of Fe with Cu-containing sites and CeOx domains, efficiently enhancing both the reoxidation of Cu+ in Cu+–Ov–Ce3+ moieties and the reducibility of Ce4+ in CeOx domains under RWGS conditions. Detailed mechanistic studies reveal that the RWGS reaction predominantly proceeds via the redox mechanism.

… understanding of the reaction mechanism taking place … mechanisms were proposed. Gorte and co-workers [12], [13], [18], [19] and Li and co-workers [20] proposed a redox mechanism …

The reaction mechanism of the reverse water–gas shift (RWGS) reaction was investigated using two commercial gold-based catalysts supported on Al2O3 and TiO2. The surface species formed during the reaction and reaction mechanisms were elucidated by transient and steady-state operando DRIFTS studies. It was revealed that RWGS reaction over Au/Al2O3 proceeds through the formation of formate intermediates that are reduced to CO. In the case of the Au/TiO2 catalyst, the reaction goes through a redox mechanism with the suggested formation of hydroxycarbonyl intermediates, which further decompose to CO and water. The Ti3+ species, the surface hydroxyls, and oxygen vacancies jointly participate. The absence of carbonyl species adsorbed on gold particles during the reaction for both catalysts indicates that the reaction pathway involving dissociative adsorption of CO2 on Au particles can be discarded. To complete the study, operando ultraviolet–visible spectroscopy was successfully applied to confirm the presence ...

Selective conversion of CO2 to CO via the reverse water gas shift (RWGS) reaction is an attractive CO2 conversion process, which may be integrated with many industrial catalytic processes such as Fischer−Tropsch synthesis to generate added value products. The development of active and cost friendly catalysts is of paramount importance. Among the available catalyst materials, transition metal phosphides (TMPs) such as MoP and Ni2P have remained unexplored in the context of the RWGS reaction. In the present work, we have employed density functional theory (DFT) to first investigate the stability and geometries of selected RWGS intermediates on the MoP (0001) surface, in comparison to the Ni2P (0001) surface. Higher adsorption energies and Bader charges are observed on MoP (0001), indicating better stability of intermediates on the MoP (0001) surface. Furthermore, mechanistic investigation using potential energy surface (PES) profiles showcased that both MoP and Ni2P were active toward RWGS reaction with the direct path (CO2* → CO* + O*) favorable on MoP (0001), whereas the COOH-mediated path (CO2* + H* → COOH*) favors Ni2P (0001) for product (CO and H2O) gas generation. Additionally, PES profiles of initial steps to CO activation revealed that direct CO decomposition to C* and O* is favored only on MoP (0001), while H-assisted CO activation is more favorable on Ni2P (0001) but could also occur on MoP (0001). Furthermore, our DFT calculations also ascertained the possibility of methane formation on Ni2P (0001) during the RWGS process, while MoP (0001) remained more selective toward CO generation.

… 2 hydrogenation reactions [7]. Additionally, the production of CO via RWGS reaction may be … However, the RWGS reaction is always accompanied by a competitive methanation process …

… We studied the mechanism of the reverse water gas shift reaction (RWGS; … reaction pathways relevant to the RWGS reaction as follows: the redox mechanism, the carboxyl mechanism, …

… Exploration of highly selective catalysts for the reverse water-gas shift reaction, which … supported metal catalysts with density functional calculations. We identified that a high selectivity …

… Meanwhile, the catalytic performance changes from the methanation reaction with 100% CH 4 over bare surface metallic Ru sites to the RWGS reaction with >99% CO selectivity over …

… as a reverse Water Gas Shift (rWGS) catalyst producing mainly CO and approaching rWGS … of the support and the decrease of the available surface area fraction for cobalt dispersion. …

Conversion of CO2 into chemicals is a promising strategy for CO2 utilization, but its intricate transformation pathways and insufficient product selectivity still pose challenges. Exploiting new catalysts for tuning product selectivity in CO2 hydrogenation is important to improve the viability of this technology, where reverse water-gas shift (RWGS) and methanation as competitive reactions play key roles in controlling product selectivity in CO2 hydrogenation. So far, a series of metal-based catalysts with adjustable strong metal–support interactions, metal surface structure, and local environment of active sites have been developed, significantly tuning the product selectivity in CO2 hydrogenation. Herein, we describe the recent advances in the fundamental understanding of the two reactions in CO2 hydrogenation, in terms of emerging new catalysts which regulate the catalytic structure and switch reaction pathways, where the strong metal–support interactions, metal surface structure, and local environment of the active sites are particularly discussed. They are expected to enable efficient catalyst design for minimizing the deep hydrogenation and controlling the reaction towards the RWGS reaction. Finally, the potential utilization of these strategies for improving the performance of industrial catalysts is examined.

… the catalytic activity and selectivity toward CO in RWGS reaction, … supported Ru NPs toward selective CO2 reduction [57]. Ceria-supported Ru NPs act as selective methanation catalysts …

… 2 , achieving selective rWGS with conventional supported metal catalysts is challenging owing … that selective rWGS can be achieved by modifying an Al 2 O 3 -supported Pd catalyst with …

Mo2C supported on nonreducible metal oxides shows increased activity for the reverse water gas shift reaction compared to reducible oxides.

Abstract Platinum (Pt)-based catalysts often failed to possess high CO2 conversion and high CO selectivity at the same time (especially at high reaction temperature) in reverse water gas shift (RWGS) reaction. Herein, we found that atomically dispersed Pt species was the crucial factor in improving the selectivity of CO and inhibiting the formation of CH4. Three Pt/CeO2 catalysts, including atomically dispersed Pt species, and Pt clusters or particles with different sizes, were synthesized. It was found that the atomically dispersed Pt/CeO2 catalyst led to an outstanding CO selectivity (> 98%) in the temperature range of 200∼450 °C, while the CO selectivities over Pt nanoparticles decreased conspicuously as the reaction temperature increased. CO-TPD and in situ FTIR experiments demonstrated that CH4 was produced by the further hydrogenation of CO. And the atomically dispersed Pt species had the relatively weak adsorption strength toward CO, which prevented excessive hydrogenation and promoted CO selectivity in RWGS reaction. Our investigation provides a new thinking for designing the RWGS reaction catalyst with an outstanding CO selectivity and emphasize the significance of atomically dispersed catalysts in catalytic reactions again.

… reverse water gas shift (RWGS) reaction is very sensitive to the metal particle size and metal-support … for the preparation of highly dispersed nickel catalyst supported on silica. The Ni …

Abstract It is desirable but challenging to obtain high methanol selectivity in CO2 hydrogenation on Cu/ZnO catalysts. Herein, we dispersed a commercial Cu/ZnO/Al2O3 on a silica support for CO2 hydrogenation to methanol, and discovered by high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM) that the distance between Cu nanoparticles on silica tuned the total methanol selectivity from 35.5 mol% to 88.9 mol%. This distance effect of Cu was elucidated by H2-TPR, FT-IR, in situ DRIFT, and catalyst silylation modification. It was identified that the active hydrogen species produced on Cu diffuse onto silica via the surface silanols, promoting reverse water gas shift (RWGS) reaction to produce CO. The average concentration of spilled hydrogen species was decreased along with the distance of Cu on silica, suppressing RWGS reaction and thus highlighting methanol selectivity. We anticipate that the distance effect observed here is prevalent on metal supported catalysts in other (de)hydrogenation reactions.

Abstract Understanding the differences between reactions driven by elevated temperature or electric potential remains challenging, largely due to materials incompatibilities between thermal catalytic and electrocatalytic environments. We show that Ni, N‐doped carbon (NiPACN), an electrocatalyst for the reduction of CO 2 to CO (CO 2 R), can also selectively catalyze thermal CO 2 to CO via the reverse water gas shift (RWGS) representing a direct analogy between catalytic phenomena across the two reaction environments. Advanced characterization techniques reveal that NiPACN likely facilitates RWGS on dispersed Ni sites in agreement with CO 2 R active site studies. Finally, we construct a generalized reaction driving‐force that includes temperature and potential and suggest that NiPACN could facilitate faster kinetics in CO 2 R relative to RWGS due to lower intrinsic barriers. This report motivates further studies that quantitatively link catalytic phenomena across disparate reaction environments.

Climate change concerns demand for drastic measures to mitigate greenhouse gas (GHG) emissions from fossil resources particularly those of CO2. Effective conversion of CO2 into syngas (a mixture of CO and H2) via reverse water gas shift (RWGS) reaction requires high temperatures (> 900 °C) to overcome thermodynamic limitations. Challenges may arise in commercial catalytic reactors in achieving close to equilibrium efficiencies due to physical barriers such as maximum catalyst operating temperature and associated operating costs. Herein, a simple and novel approach is presented to produce syngas from CO2 via RWGS reaction using a high temperature hydrogen oxyflame. Test results from a tubular laboratory reactor show that a CO2 conversion of up to 75 % is achievable in a single pass with a gas residence time of < 0.03 s. Lower than equilibrium CO2 conversions are observed due to non-adiabatic temperatures in the reactor. Heat integration and reactor insulation at industrial scale would help in a closer to equilibrium performance. Systematic analysis of reactor performance supported by empirical modelling revealed that there is an optimum economical point where hydrogen consumption can be minimized (< 1.0 mol H2/mol CO2). A trade-off must be made to identify an optimum operating point depending on required syngas quality. Relatively small effect of reactor wall material (within 10 % in CO2 conversion) may indicate an enhancing effect of hydrogen oxyflame as the main contributor to the reactor performance.

Transformation of CO2 into value-added products via photothermal catalysis has become an increasingly popular route to help ameliorate the energy and environmental crisis derived from the continuing use of fossil fuels, as it can integrate light into well-established thermocatalysis processes. The question however remains whether negative CO2 emission could be achieved through photothermal catalytic reactions performed in facilities driven by electricity mainly derived from fossil energy. Herein, we propose universal equations that describe net CO2 emissions generated from operating thermocatalysis and photothermal reverse water-gas shift (RWGS) and Sabatier processes for batch and flow reactors. With these reactions as archetype model systems, the factors that will determine the final amount of effluent CO2 can be determined. The results of this study could provide useful guidelines for the future development of photothermal catalytic systems for CO2 reduction.

In recent years, the combination of both thermal and photochemical contributions has provided interesting opportunities for solar upgrading of catalytic processes. Photothermal catalysis works at the interface between purely photochemical processes, which involve the direct conversion of photon energy into chemical energy, and classical thermal catalysis, in which the catalyst is activated by temperature. Thus, photothermal catalysis acts in two different ways on the energy path of the reaction. This combined catalysis, of which the fundamental principles will be reviewed here, is particularly promising for the activation of small reactive molecules at moderate temperatures compared to thermal catalysis and with higher reaction rates than those attained in photocatalysis, and it has gained a great deal of attention in the last years. Among the different applications of photothermal catalysis, CO_2 conversion is probably the most studied, although reaction mechanisms and photonic-thermal synergy pathways are still quite unclear and, from the reaction route point of view, it can be said that photothermal-catalytic CO_2 reduction processes are still in their infancy. This article intends to provide an overview of the principles underpinning photothermal catalysis and its application to the conversion of CO_2 into useful molecules, with application essentially as fuels but also as chemical building blocks. The most relevant specific cases published to date will be also reviewed from the viewpoint of selectivity towards the most frequent target products.

Abstract Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift (RWGS) reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization efficiency while generating CH4 as a by-product. In this work, a homogeneously dispersed molybdenum carbide hybrid catalyst with sub-nanosized cluster (the average size as small as 0.5 nm) is prepared via a facile carbothermal treatment for highly selective CO2–CO reduction. The partially disordered Mo2C clusters are characterized by synchrotron high-resolution XRD and atomic resolution HAADF-STEM analysis, for which the source cause of the disorder is pinpointed by XAFS analysis to be the nitrogen intercalants from the carbonaceous precursor. The partially disordered Mo2C clusters show a RWGS rate as high as 184.4  μ mol g M o 2 C − 1 s − 1 at 400 °C with a superior selectivity toward CO (> 99.5%). This work highlights a facile strategy for fabricating highly dispersed and partially disordered Mo2C clusters at a sub-nano size with beneficial N-doping for delivering high catalytic activity and operational stability.

11 CO 2 utilization via reverse water gas shift (rWGS) reaction has been proposed as a path to the 12 sustainable utilization . This work presents a detailed process modelling study where steam 13 methane reforming (SMR) generated hydrogen was combined with rWGS to produce syngas 14 (CO+H 2 ) with various hydrogen-to-carbon oxide ratios. To further decrease CO 2 emissions that 15 may offset the benefits of CO 2 converted in rWGS, electrification of endothermal reactors, both 16 SMR and rWGS was considered where CO 2 emitting fuel burning in the furnace was replaced by 17 the emerging ohmic (resistive) heating. Material and energy inventory obtained from process 18 design calculations was used to perform Life Cycle Analysis (LCA) to calculate environmental 19 impacts of CO 2 consumption and reactor electrification. The results showed that greenhouse gas 20 emissions, in CO 2 kg equivalent, were the lowest when both SMR and rWGS were heated using 21 wind-generated electricity , decreasing from 25 to 10 kg CO 2 equivalent for H 2 :CO=2:1 while 22 the conventional electricity mix used for furnace electrical heating across the board of scenarios 23 generated highest environmental impacts, much higher than those that used natural gas as fuel. 24 Process economics calculations suggested that, when both SMR and rWGS were electrically 25 heated, the process only showed product syngas cost parity with the conventional fuel heated 26 design when electricity cost was ~$0.008/kWh. This suggests that CO 2 utilization scenarios 27 involving process electrification need to be carefully considered from the total design perspective

… photo-thermal catalytic reverse water–gas shift (RWGS) reaction. … TiO 2 for photo-thermal catalytic RWGS reaction. The catalytic … , photo-to-thermal conversion efficiency evaluation and …

In the context of CO2 valorisation, the reverse water–gas shift reaction (RWGS) is gathering momentum since it represents a direct route for CO2 reduction to CO. The endothermic nature of the reaction posses a challenge when it comes to process energy demand making necessary the design of effective low-temperature RWGS catalysts. Herein, multicomponent Cs-promoted Cu, Ni and Pt catalysts supported on TiO2 have been studied in the low-temperature RWGS. Cs resulted an efficient promoter affecting the redox properties of the different catalysts and favouring a strong metal-support interaction effect thus modulating the catalytic behaviour of the different systems. Positive impact of Cs is shown over the different catalysts and overall, it greatly benefits CO selectivity. For instance, Cs incorporation over Ni/TiO2 catalysts increased CO selectivity from 0 to almost 50%. Pt-based catalysts present the best activity/selectivity balance although CuCs/TiO2 catalyst present comparable catalytic activity to Pt-studied systems reaching commendable activity and CO selectivity levels, being an economically appealing alternative for this process.

… /CO 2 ratios, and various gas hourly space velocities (GHSV) at atmospheric pressure were assessed. In this study, excellent CO 2 conversion was … in terms of CO 2 conversion and CO …

Utilization of CO 2 is a requirement for a sustainable production of carbon-based chemicals. Reverse water-gas-shift (RWGS) can valorize CO 2 by reaction with hydrogen to produce a synthesis gas compatible with existing industrial infrastructure. Fully electrified reverse water-gas-shift (eRWGS™) was achieved using integrated ohmic heating and a nickel type catalyst at industrially relevant conditions. Using a feed of H 2 :CO 2 in a ratio of 2.25 at 10 barg, utilizing high temperature operation at 1050°C allowed for production of a synthesis gas with a H 2 /CO ratio of 2.0 and no detectable methane, ideal for production of sustainable fuel by e.g. the Fischer-Tropsch synthesis. Facilitating RWGS through CH 4 as intermediate was found superior to the selective RWGS route, due to higher activity and suppression of carbon formation. The eRWGS™ catalyst is found to provide a preferential emissions free route for production of synthesis gas for any relevant H 2 /CO ratio, enabling production of sustainable carbon-based chemicals from CO 2 and renewable electricity with high hydrogen and carbon efficiency.

… prepared for CO 2 conversion to CO by auto-thermal catalyst-assisted chemical looping. This process is designed to maximize CO 2 conversion. The generation of CO from CO 2 was …

… to achieve efficient photo-thermal performance in the RWGS reaction. The incorporation of Pt, … photo-thermal RWGS reaction. The optimized catalysts exhibited a high CO 2 conversion (…

Abstract Fe-based catalysts are efficient systems for CO2 conversion via reverse water-gas shift (rWGS) reaction. Nevertheless, the nature of the active phase, namely metallic iron, iron oxide or iron carbide remains a subject of debate which our paper is meant to close. Fe0 is a much better catalyst for the rWGS than Fe3C. The activity of Fe0 can be promoted by the addition of Cs and Cu whose presence hinders iron carburisation while favouring both higher conversion and enhanced selectivity. When the samples are aged in the rWGS reaction mixture during stability test a new phase appear: Fe5C2, resulting in a more active but less selective catalysts than Fe0 for the rWGS reaction. Hence our results indicate that we could potentially achieve an optimal activity/selective balance upon finely tuning the proportion Fe/Fe5C2. Beyond the fundamental information concerning active phase we have observed the presence of advanced Fischer-Tropsch-like products at ambient pressure opening new opportunities for the design of hybrid rWGS/Fischer-Tropsch systems.

… a remarkable improvement from thermal equilibrium limits. To … thermal management, providing a scalable and energy-efficient framework for the valorization of anthropogenic CO 2 …

… of two different precursor reactant materials by heating in diverse gas mixtures is reported … The conversions of CO 2 during the reverse water–gas shift (RWGS) were calculated for all …

Abstract Photothermal reverse-water-gas-shift is realized with high conversion rate and selectivity of CO in the case of Au/CeO2 catalyst. Moreover, photothermal reaction rate is much higher (>10 times) than that performed under thermal condition. As indicated by the results of in-situ infrared spectroscopy and kinetic experiments, the special role of light is found to be related with the promotion of hydrogen-splitting step. The robust Au/CeO2 catalyst exhibits stable activity and CO selectivity under long-term light irradiation. It is expected that the combination of catalysts and light may afford new perspectives for the CO2 hydrogenation.

… Looping Reverse Water Gas Shift (CLRWGS) process as a viable route for sustainable CO2 … to decouple the conversion–selectivity interplay of the conventional RWGS reaction, …

Catalytic conversion of CO2 into chemicals and fuels is a viable method to reduce carbon emissions and achieve carbon neutrality. Through thermal catalysis, electrocatalysis, and photo(electro)catalysis, CO2 can be converted into a wide range of valuable products, including CO, formic acid, methanol, methane, ethanol, acetic acid, propanol, light olefins, aromatics, and gasoline, as well as fine chemicals. In this mini-review, we summarize the recent progress in heterogeneous catalysis for CO2 conversion into chemicals and fuels and highlight some representative studies of different conversion routes. The structure–performance correlations of typical catalytic materials used for the CO2 conversion reactions have been revealed by combining advanced in situ/operando spectroscopy and microscopy characterizations and density functional theory calculations. Catalytic selectivity toward a single CO2 reduction product/fraction should be further improved at an industrially relevant CO2 conversion rate with considerable stability in the future.

… TPR) experiments with a thermal conductivity detector (TCD) … converting CO back to CO 2 , due to the high oxygen mobility, which increases the rate of WGS more than the rate of RWGS …

… CO 2 , offering a dominant plasma-assisted surface reaction pathway for the improved reverse water-gas shift … environments to facilitate efficient plasma-assisted catalytic reactions, with …

… one while preserving the H 2 /CO 2 feed molar ratio equal to 3. The mechanism of the plasma-assisted RWGS reaction initially involves the dissociation of CO 2 , causing the generation …

CO2 and CH4 contribute to greenhouse gas emissions, while the production of industrial base chemicals from natural gas resources is emerging as well. Such conversion processes, however, are energy-intensive and introducing a renewable and sustainable electric activation seems optimal, at least for intermediate-scale modular operation. The review thus analyses such valorisation by plasma reactor technologies and heterogeneous catalysis application, largely into higher hydrocarbon molecules, that is ethane, ethylene, acetylene, propane, etc., and organic oxygenated compounds, i.e. methanol, formaldehyde, formic acid and dimethyl ether. Focus is given to reaction pathway mechanisms, related to the partial oxidation steps of CH4 with O2, H2O and CO2, CO2 reduction with H2, CH4 or other paraffin species, and to a lesser extent, to mixtures' dry reforming to syngas. Dielectric barrier discharge, corona, spark and gliding arc sources are considered, combined with (noble) metal materials. Carbon (C), silica (SiO2) and alumina (Al2O3) as well as various catalytic supports are examined as precious critical raw materials (e.g. platinum, palladium and rhodium) or transition metal (e.g. manganese, iron, cobalt, nickel and copper) substrates. These are applied for turnover, such as that pertinent to reformer, (reverse) water–gas shift (WGS or RWGS) and CH3OH synthesis. Time-on-stream catalyst deactivation or reactivation is also overviewed from the viewpoint of individual transient moieties and their adsorption or desorption characteristics, as well as reactivity.

… conversion reached up to ~90% in the plasma core (CO 2 /H 2 with … These findings highlight that efficient CO 2 dissociation and … -driven RWGS as a promising route for CO 2 utilization …

Plasma-catalytic CO2 hydrogenation to CO offers a promising route for carbon-neutral chemical synthesis. However, its advancement is constrained by low energy efficiency and limited mechanistic insight. Here, we developed an oxygen vacancy-engineered Pd-WO3–x catalyst supported on nickel foam (NF), which exhibits enhanced performance in ambient plasma-driven CO2 conversion. The system leverages the conductive properties of NF to spatially divide the discharge zone into streamer and filamentary discharge zones, thereby enhancing plasma activation and interfacial charge transfer. Catalyst characterization reveals that Pd plays a critical role in stabilizing metastable oxygen vacancies (OVs) within WO3–x , which function as electron reservoirs to promote CO2 dissociation into CO. Density functional theory calculations and in situ spectroscopic studies confirm that Pd facilitates H2 dissociation, while vibrationally excited CO2 generated in the plasma gas phase preferentially adsorbs at OV sites. At a specific energy input of 33.6 kJ L–1, the system demonstrates superior performance, achieving 54.9% CO2 conversion with 99.8% selectivity toward CO, surpassing typical plasma-catalytic benchmarks. The catalyst exhibited good stability over 100 h of continuous operation, with a slight decrease in CO2 conversion (<10%) and nearly unchanged CO selectivity (>99%) due to strong metal–support interactions and the conductive nature of NF. This work demonstrates that OV engineering provides a promising strategy for designing efficient plasma-catalytic systems for CO2 conversion.

… The rational design of efficient catalysts for the plasma-assisted RWGS reaction is impeded by an incomplete understanding of the molecular activation mode and underlying reaction …

… at atmospheric pressure, the RWGS reaction may have higher CO 2 conversion than the … the main components of CO 2 , CO, and H 2 in the dry gas after the RWGS reaction. The mass …

… reaction between CO 2 and hydrogen tends to favor the reverse water–gas shift (RWGS) reaction, … (52) explored the mechanism of the Cu 13 /γ-Al 2 O 3 catalyst in plasma-assisted CO 2 …

Plasma-catalytic CO2 hydrogenation is a complex chemical process combining plasma-assisted gas-phase and surface reactions. Herein, we investigated CO2 hydrogenation over Pd/ZnO and ZnO in a tubular dielectric barrier discharge (DBD) reactor at ambient pressure. Compared to the CO2 hydrogenation using Plasma Only or Plasma + ZnO, placing Pd/ZnO in the DBD almost doubled the conversion of CO2 (36.7%) and CO yield (35.5%). The reaction pathways in the plasma-enhanced catalytic hydrogenation of CO2 were investigated by in situ Fourier transform infrared (FTIR) spectroscopy using a novel integrated in situ DBD/FTIR gas cell reactor, combined with online mass spectrometry (MS) analysis, kinetic analysis, and emission spectroscopic measurements. In plasma CO2 hydrogenation over Pd/ZnO, the hydrogenation of adsorbed surface CO2 on Pd/ZnO is the dominant reaction route for the enhanced CO2 conversion, which can be ascribed to the generation of a ZnOx overlay as a result of the strong metal–support interactions (SMSI) at the Pd–ZnO interface and the presence of abundant H species at the surface of Pd/ZnO; however, this important surface reaction can be limited in the Plasma + ZnO system due to a lack of active H species present on the ZnO surface and the absence of the SMSI. Instead, CO2 splitting to CO, both in the plasma gas phase and on the surface of ZnO, is believed to make an important contribution to the conversion of CO2 in the Plasma + ZnO system.

… kinetic and thermodynamic driving forces through simulated carbon selectivity for a hypothetical catalyst formulation on which methanol synthesis, RWGS… The formation of CO via RWGS …

… and postulated that this change in kinetics may be attributed to a … studied the kinetics of the reverse water-gas shift reaction over … has on the kinetics of the RWGS reaction over typical …

… The WGS and/or RWGS reactions are readily … the kinetics of the RWGS reaction over platinum in 1925 [6]. For both WGS and RWGS reactions, Amenomiya investigated the kinetics of …

… RWGS‐CL is most beneficial for the production of pure CO, where the StS efficiency is one percent point higher compared to that of the RWGS … The StS efficiencies for RWGS and RWGS…

… As expected, r CO increases with temperature, and the low-conversion conditions ensure that these trends represent intrinsic kinetics rather than being influenced by thermodynamic …

… selected based on the thermodynamic stability, determined … In particular, efficient RWGS conversion at 1 atm typically … in governing the reaction kinetics of RWGS, providing critical …

Abstract The reverse water gas shift (RWGS) reaction is a method of converting waste CO2 and renewable H2 to CO and H2O, where the resulting CO can be used in processes requiring syngas. This paper presents lab-scale data collected for RWGS on a Nickel catalyst coated monolith reactor, along with 3D modeling with ANSYS FLUENT and DUO (DETCHEMTM + OpenFOAM coupling) computational fluid dynamics software. Using a 42-step previously published mechanism, the software accurately predicts the outlet concentrations of H2, H2O, CO and CO2 at two inlet flow rates. CH4 is underpredicted and the experimental data shows effectively complete conversion closer to the front-end of the catalyst than do the simulations. This may be due to inaccuracies in the measurement of the catalyst loading ( F c a t / g e o value), because if a higher F c a t / g e o is assumed the simulation more closely matches the experimental results. Further, DUO and FLUENT results fit very well, and both codes are able to predict the general trend of significant species diffusion ahead of the monolith using the mixture averaged diffusion assumption. Ultimately, heat transfer with the monolith solid structure is inherently important, and thus isothermal calculations more closely match experimental values than do those with adiabatic boundary conditions. To better capture the thermal profile within the various channels it is necessary to model a 3D quarter monolith section.

… This analysis, supported by thermodynamic … RWGS reactions in relation to temperature. The investigation reveals a temperature transition zone around 850 C where WGS and RWGS …

… IL-based RWGS system. However, so far, the thermodynamic influence of ILs on the RWGS … ILs can have a substantial impact not only on reaction kinetics but also on thermodynamics. …

… The reverse-water-gas-shift reactor and the methanol synthesis reactor were serially aligned … CO and water by the reverse-water-gas-shift reaction (RWReaction) to remove water before …

… However, synthesis of methanol from CO 2 needs a relatively high pressure and low temperature to minimize the reverse water–gas shift reaction. Direct CO 2 hydrogenation to formic …

Due to increasing worldwide fossil fuel consumption, carbon dioxide levels have increased in the atmosphere with increasingly important impacts on the environment. Renewable and clean sources of energy have been proposed, including wind and solar, but they are intermittent and require efficient and scalable energy storage technologies. Electrochemical CO2 reduction reaction (CO2RR) provides a valuable approach in this area. It combines solar- or wind-generated electrical production with energy storage in the chemical bonds of carbon-based fuels. It can provide ways to integrate carbon capture, utilization, and storage in energy cycles while maintaining controlled levels of atmospheric CO2. Electrochemistry allows for the utilization of an electrical input to drive chemical reactions. Because CO2 is kinetically inert, highly active catalysts are required to decrease reaction barriers sufficiently so that reaction rates can be achieved that are sufficient for electrochemical CO2 reduction. Given the reaction barriers associated with multiple electron-proton reduction of CO2 to CO, formaldehyde (HC(O)H), formic acid, or formate (HC(O)OH, HC(O)O-), or more highly reduced forms of carbon, there is also a demand for high selectivity in catalysis. Catalysts that have been explored include homogeneous catalysts in solution, catalysts immobilized on surfaces, and heterogeneous catalysts. In homogeneous catalysis, reduction occurs following diffusion of the catalyst to an electrode where multiple proton coupled electron transfer reduction occurs. Useful catalysts in this area are typically transition-metal complexes with organic ligands and electron transfer properties that utilize combinations of metal and ligand redox levels. As a way to limit the amount of catalyst, in device-like configurations, catalysts are added to the surfaces of conductive substrates by surface binding, in polymeric films, or on carbon electrode surfaces with molecular structures and electronic configurations related to catalysts in solution. Immobilized, homogeneous catalysts can suffer from performance losses and even decomposition during long-term CO2 reduction cycles, but they are amenable to detailed mechanistic investigations. In parallel efforts, heterogeneous nanocatalysts have been explored in detail with the development of facile synthetic procedures that can offer highly active catalytic surface areas. Their high activity and stability have attracted a significant level of investigation, including possible exploitation for large-scale applications. However, translation of catalytic reactivity to the surface creates a new reactivity environment and complicates the elucidation of mechanistic details and identification of the active site in exploring reaction pathways. Here, the results of previous studies based on transition-metal complex catalysts for CO2 electroreduction are summarized. Early studies showed that transition-metal complexes of Ru, Ir, Rh, and Os, with well-defined structures, are all capable of catalyzing CO2 reduction to CO or formate. Derivatives of the complexes were surface attached to conducting electrodes by chemical bonding, noncovalent bonding, or polymerization. The concept of surface binding has also been extended to the preparation of surface area electrodes by the chemically controlled deposition of nanostructured catalysts such as nano tin, nano copper, and nano carbon, all of which have been shown to have high selectivities and activities toward CO2 reduction. In our presentation, we end this Account with recent advances and a perspective about the application of electrocatalysis in carbon dioxide reduction.

Electrochemical reduction of carbon dioxide (CO2) to fuels and chemicals provides a promising solution for renewable energy storage and utilization. Among the many possible reaction pathways, CO2 conversion to carbon monoxide (CO) is the first step in the synthesis of more complex carbon‐based fuels and feedstocks, and holds great significance for the chemical industry. Herein, recent advances in heterogeneous catalysts for selective CO evolution from electrochemical reduction of CO2 are described. With Au catalysts as a paradigm, principles for catalyst design including size, morphology, and grain boundary densities tuning, surface modifications, as well as metal‐support interaction are comprehensively summarized, which shed light on the development of other transition metal catalysts targeting efficient CO2‐to‐CO conversion. In addition, recently emerged novel materials including transition metal single‐atom catalysts, which present significantly different catalytic behaviors compared to their bulk counterparts and thus open up many unexpected opportunities, are summarized. Furthermore, the technical aspects with respect to large‐scale production of CO are presented, focusing on the full‐cell design and implementation. Finally, short comments related to the future direction of real‐word CO2 electrolysis for CO supply are provided in terms of catalyst optimization and technical breakthrough.

… the presence of CO 2 promotes the electrochemical CO reduction reaction, … CO2 ) more active in the CO 2 -to-CO conversion and the other (Cu CO ) favouring the further reduction of CO …

… The catalytic reduction of CO 2 /CO is key to reducing the … similarities of the CO 2 /CO catalytic reduction reactions in gas, … allows catalysts to be categorized by reduction products. The …

Traditional catalytic techniques often encounter obstacles in the search for sustainable solutions for converting CO2 into value-added products because of their high energy consumption and expensive catalysts. Here, we introduce a contact-electro-catalysis approach for CO2 reduction reaction, achieving a CO Faradaic efficiency of 96.24%. The contact-electro-catalysis is driven by a triboelectric nanogenerator consisting of electrospun polyvinylidene fluoride loaded with single Cu atoms-anchored polymeric carbon nitride (Cu-PCN) catalysts and quaternized cellulose nanofibers (CNF). Mechanistic investigation reveals that the single Cu atoms on Cu-PCN can effectively enrich electrons during contact electrification, facilitating electron transfer upon their contact with CO2 adsorbed on quaternized CNF. Furthermore, the strong adsorption of CO2 on quaternized CNF allows efficient CO2 capture at low concentrations, thus enabling the CO2 reduction reaction in the ambient air. Compared to the state-of-the-art air-based CO2 reduction technologies, contact-electro-catalysis achieves a superior CO yield of 33 μmol g−1 h−1. This technique provides a solution for reducing airborne CO2 emissions while advancing chemical sustainability strategy. Traditional catalytic techniques often encounter obstacles in the search for sustainable solutions for converting CO2 into value-added products because of their high energy consumption and expensive catalysts. Here, we introduce a contact-electro-catalysis approach for CO2 reduction reaction, achieving CO Faradaic efficiency of 96.24%.

… showed greatly enhanced activity for the aqueous electrochemical reduction of CO 2 to CO. … In this context, molecular catalysts for electrochemical CO 2 conversions can be …

… photocatalysts for catalytic CO 2 reduction remains a big … CO 2 reduction activity of various perovskite oxides (BiFeO 3 , LaFeO 3 and LaNiO 3 ) with an inactive CO 2 photo-reduction …

The performance of a water-soluble cobalt porphyrin ([{meso-tetra(4-sulfonatophenyl)porphyrinato}cobalt(III)], CoTPPS) as a catalyst for the photoreduction of CO2 in fully aqueous media has been investigated under visible light irradiation using [Ru(bpy)3]2+ as a photosensitizer and ascorbate as a sacrificial electron donor. CO is selectively produced (>82%) with high efficiency (926 TONCO; TONCO = turnover number for CO). Upon optimization, selectivities of at least 91% are achieved. Efficiencies up to 4000 TONCO and 2400 h–1 TOFCO (TOFCO = turnover frequency for CO) are reached at low catalyst loadings, albeit with loss in selectivity. This work successfully demonstrates the ability of CoTPPS to perform highly efficient photoreduction of CO2 in water while retaining its high selectivity for CO formation.

The electrochemical reduction of CO2 to give CO in the presence of O2 would allow the direct valorization of flue gases from fossil fuel combustion and of CO2 captured from air. However, it is a challenging task because O2 reduction is thermodynamically favored over that of CO2. 5% O2 in CO2 near catalyst surface is sufficient to completely inhibit the CO2 reduction reaction. Here we report an O2-tolerant catalytic CO2 reduction electrode inspired by part of the natural photosynthesis unit. The electrode comprises of heterogenized cobalt phthalocyanine molecules serving as the cathode catalyst with >95% Faradaic efficiency (FE) for CO2 reduction to CO coated with a polymer of intrinsic microporosity that works as a CO2-selective layer with a CO2/O2 selectivity of ∼20. Integrated into a flow electrolytic cell, the hybrid electrode operating with a CO2 feed gas containing 5% O2 exhibits a FECO of 75.9% with a total current density of 27.3 mA/cm2 at a cell voltage of 3.1 V. A FECO of 49.7% can be retained when the O2 fraction increases to 20%. Stable operation for 18 h is demonstrated. The electrochemical performance and O2 tolerance can be further enhanced by introducing cyano and nitro substituents to the phthalocyanine ligand.

… compositions, high surface area, elevated CO 2 adsorption capability, and adjustable active … materials for catalytic CO 2 conversion. The significance of the conversion of CO 2 is carried …

… , and derivatives thereof were investigated as electrocatalytic CO 2 reduction catalysts 58 . COF-366-Co was demonstrated to reduce CO 2 in water at an overpotential of –0.55 V, …

Abstract Carbon dioxide (CO2) hydrogenation to value-added molecules is an attractive way to reduce CO2 emission via upgrading. Herein, non-thermal plasma (NTP) activated CO2 hydrogenation over Ru/MgAl layered double hydroxide (LDH) catalysts was performed. The catalysis under the NTP conditions enabled significantly higher CO2 conversions (∼85 %) and CH4 yield (∼84 %) at relatively low temperatures compared with the conventional thermally activated catalysis. Regarding the catalyst preparation, it was found that the reduction temperature can affect the chemical state of the metal and metal-support interaction significantly, and thus altering the activity of the catalysts in NTP-driven catalytic CO2 hydrogenation. A kinetic study revealed that the NTP-catalysis has a lower activation energy (at ∼21 kJ mol−1) than that of the thermal catalysis (ca. 82 kJ mol−1), due to the alternative pathways enabled by NTP, which was confirmed by the comparative in situ diffuse reflectance infrared Fourier (DRIFTS) coupled with mass spectrometry (MS) characterisation of the catalytic systems.