Water Gas Shift Research Articles

In‐Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water‐Gas Shift Reaction

AbstractIn situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water‐gas shift (RWGS) reaction. Surface oxygen atoms in various Mo‐based catalysts are removed in H2‐containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt‐dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal−1 ⋅ h−1 at 600 °C has been achieved over in situ carbonized H‐intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

Active Learning Guided Discovery of High Entropy Oxides Featuring High H2-production.

High entropy oxides (HEOs) represent a class of solid solutions comprising multiple elements, offering significant scientific potential. Due to the enormous combination types of elements, the design of HEOs with desirable properties within high-dimensional composition spaces has traditionally relied heavily on knowledge and intuition. In this study, we present an active learning (AL) strategy tailored to efficiently explore the vast compositional space of HEOs. Our approach operates as a closed-loop system, iteratively cycling through "Training, Prediction, and Experiment" stages. Across multiple AL iterations, we have successfully identified four novel HEOs from a vast array of potential compositions. These newly discovered materials exhibit exceptional stability and demonstrate outstanding performance in H2 evolution rate (251 μmol gcat-1 min-1) during the water-gas shift reaction, surpassing benchmarks set by established catalysts such as Pt/γ-Al2O3 (135 μmol gcat-1 min-1) and Cu/ZnO/Al2O3 (81 μmol gcat-1 min-1). X-ray photoelectron spectroscopy and density functional theory calculations revealed a loss of elemental identity in the selected HEOs. This catalyst discovery process underscores the efficacy of Machine Learning in accelerating the identification of HEOs with unique characteristics by effectively leveraging insights from limited experimental data.

Insights into Mechanisms of Reverse Water Gas Shift Activity Enhancement over Reverse Microemulsion‐Synthesized CuCeO2

AbstractCopper‐doped ceria (CuCeO2) catalysts with 0–26.5 Cu/(Cu+Ce) at% were synthesized via the reverse microemulsion method. X‐ray diffraction analysis of freshly synthesized and spent (post‐reaction) catalysts showed no separate phase of copper or copper oxide, indicating that Cu was incorporated into the CeO2 lattice, replacing Ce. Temperature programmed desorption experiments showed that the activation energy of CO2 desorption increased for higher Cu loadings, indicating stronger CO2 adsorption. This phenomenon was attributed to enhanced formation of oxygen vacancies due to Cu doping. X‐ray photoelectron spectroscopy further confirmed the enhanced generation of oxygen vacancies due to Cu incorporation. Catalytic performance evaluation with the H2/CO2 feed in the 300–600 °C range showed that all catalysts were 100 % selective to CO generation, with higher Cu loadings resulting in CO2 conversion close to equilibrium values at 500–600 °C. The activation energy of the reaction, determined through reaction tests, exhibited inverse relationship with the activation energy of CO2 desorption. The relationship between these two energy barriers is explored, providing valuable insights into the mechanism of RWGS activity enhancement.

Reduction of CO2 emissions by recycling low-potential heat from the Benfield CO2 removal process at a natural gas hydrogen production plant

AbstractThe EU policies related to CO2 emission strictly define the stages of carbon neutrality achieving. According to these regulations, all production installations that emit carbon dioxide will be charged additional emission fees from 2026 to fully in 2035. Analysis of the increasing emission fees shows that in some industries incurring such additional costs will result in a lack of profitability of the products. Industries directly related to the food sector, such as nitrogen fertiliser production, are strategic in the economies of all countries. Nitrogen fertilisers are produced from ammonia, which is synthesised on a large scale from hydrogen and nitrogen. Hydrogen is produced by natural gas reforming with water vapour resulting in syngas (mixture of H2, CO, CO2, H2O), which CO in the next step reacts with water vapour (water gas shift reaction) producing H2 and CO2. CO2 is separated from hydrogen using the Benfield method. The analysis of the Benfield process (one process of hydrogen production) shows a possible way to reduce CO2 emission by optimising heat balance. It was shown that in the proposed technology the heat recovery reaches 89%, while the level below 30% was reported for other available technologies. The proposed solution is based on recirculation and reuse of heat, which is lost in other technologies. The analysis is for a process balance in a medium-sized hydrogen production installation. The analysis considers also the correlations with other installations thermally linked to hydrogen production. The economic balance showed the great financial benefits of this solution. In the scenario discussed, the CO2 emission factor was reduced by 20%. Graphical Abstract

Enhanced CO2 hydrogenation reaction by Tuning interfacial Cu/ZnOx through synergistic interactions in the precursors

The Cu/ZnO/Al2O3 is a typical industrial catalyst for water–gas-shift reaction and methanol synthesis, and is also gaining momentum in CO2 hydrogenation reaction. The dynamic evolution of the phases and microstructures of the precursor of this catalyst leads to a notable synergistic effect that defines its overall catalytic function and performance. To gain insights into the role and interaction between the relevant precursors, we compared Cu/ZnO/Al2O3 catalysts using a conventional co-precipitation and a fractional precipitation method, where the latter one shows an enhanced Cu/ZnOx interface due to a thorough and strong interaction between two components in the precursor. The ZnOx decoration on Cu with unsaturated Znδ+ species boosted the methanol formation to a rate of 508 gCH3OH‧kgcat−1‧h−1 with 58 % selectivity at 513 K and 3 MPa. This work provides mechanistic insights into the synergistic interplay between the involved phases in the Cu/ZnO/Al2O3 catalyst.

Kinetic investigation of dry reforming of methane reaction over Ni–Rh/ZrO2–Al2O3 catalyst using Langmuir-Freundlich isotherm

The study involved conducting kinetic measurements for the dry reforming of methane (DRM) over a Ni–Rh/Al2O3 (85%)-ZrO2(15%) catalyst under a wide range of operating conditions (temperature: 500–900 °C, total flow rate of the inlet feed: 50–100 mL/min). The support material was prepared using the sol-gel method, followed by impregnation of Ni–Rh catalyst on the incipient wetness of the Al2O3–ZrO2 support. The calcined, reduced and spent samples were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometer (ICP-AES), N2 adsorption/desorption and CHNS analyzer, and tested for activity, yield and stability in DRM reaction. Furthermore, kinetic behavior of Ni–Rh/Al2O3–ZrO2 catalyst in DRM process was investigated by assuming DRM and reverse water-gas shift (RWGS) reactions take place on two kinds of different active sites. Experimental data were fitted using rate expressions based on the Langmuir-Freundlich (LF) isotherm for DRM and RWGS reactions. The activation energy for the DRM reaction was optimized at 43.62 kJ/mol, falling within the reported literature range of 24.73–108.9 kJ/mol. Statistical indices indicated that the kinetic model accurately predicted CO2 conversion compared to other responses, with an error of 12.054%. The computed and experimental trends for CH4 and CO2 conversions, H2 and Co yield in terms of temperature were similar with each other and the difference between the calculated and experimental trends was lower for conversions compared to yields.

Effect of Ni/Co ratio on Ce-Sc-ZrO2 catalysts for selective H2 production via methane partial oxidation

Partial oxidation of methane (POM) is a promising route for hydrogen production, and achieving a high H2 yield with an H2/CO ratio >3 is highly appealing. Optimization of Ni/Co ratios over Ce-Sc-ZrO2 (CSZ) is investigated for POM reaction and characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed reduction/oxidation/desorption, and transmission electron microscopy. The active site derived from the reduction of “strongly interacted NiO” is responsible for the dissociation of C–H (of CH4), resulting high activity towards POM. 5Ni/CSZ has the highest amount of such active sites and attains the highest activity. 5Co/CSZ catalyst has cobalt-based active sites, and there is an inert carbon deposit during the reaction, causing the least activity. 3.75 wt% Ni and 1.25 wt% Co combination over CSZ support surges the highest density of basicity, oxide vacancy, and adequate amount of active sites derived from “strongly interacted NiO”. The active sites with enhanced metal-support interaction are further grown under exposure to oxidizing gas (O2) and reducing gas (H2) during the POM reaction. The highest density of basicity and oxide vacancy involves more CO2 and H2O in the sequential oxidation of CH4 under indirect pathways. The exclusive involvement of indirect pathways of POM and inhibition of hydrogen consuming reaction (like reverse water gas shift reaction) over 3.75Ni1.25Co/CSZ results into 48 % H2 yield and 3.26 H2/CO ratio up to 24 h time on stream at 600 °C. The H2 yield doubles to ∼97 %, and the H2/CO ratio comes close to 2 over 3.75Ni1.25Co/CSZ catalyst at 900 °C.

Nickel Dynamics Switches the Selectivity of CO2 Hydrogenation.

The Reverse Water Gas-Shift reaction (CO2 + H2=CO + H2O) allows to balance syn-gas under industrial conditions. Nickel has been suggested as a potential catalyst but the temperature required is too high, more than 800ºC, limiting practical implementation but when lowering the temperature methanation occurs. Simulations via Density Functional Theory on well-defined surfaces have systematically failed to reproduce these experimental results. But under reaction conditions Ni surfaces are not static and DFT models coupled to microkinetics show that at high CO coverages drive the generation of Ni adatoms that are the active sites for methanation. At higher temperatures, the adatom population decreases, and the selectivity towards CO increases. Thus, the mechanism behind the selectivity switch is driven by the dynamics induced by reaction intermediates. Our work contributes to the inclusion of dynamic aspects of materials under reaction conditions in the understanding of complex catalytic behaviour.

Direct liquefaction behavior of Shenhua Shangwan coal under CO containing atmosphere

Direct coal liquefaction (DCL) under CO or syngas atmosphere is beneficial to reduce the cost of hydrogen production. Effects of CO on liquefaction process of Shangwan coal were investigated by comparing the liquefaction behavior in three atmospheres of CO, H2, and N2. Then, effects of different CO/H2 ratios and catalysts on the liquefaction process in syngas were investigated. The results indicated that the oil yield under CO atmosphere reached 43.1%, which was 4.2% lower than that under H2, but 10.2% higher than that under N2. The liquefaction performance was further improved by adding the Shenhua 863 catalyst. It is analyzed that CO promoted liquefaction in two ways: water-gas shift reaction and the reaction between CO and organic structures of coal. Through characterization of the products by GC-MS and FT-IR, it was found that CO makes benzenes, aliphatics, and oxygen-containing compounds in liquefied oil simultaneously increased. The effect on functional groups and free radicals concentration in the solid products was not obvious. The experimental results under syngas showed that the highest oil yield, 57.4%, can be obtained in DCL with 20% CO syngas, and further improved by increasing moisture content of coal appropriately. In addition, the Shenhua 863 catalyst had a good catalytic effect on the liquefaction process and also water-gas shift reaction.

Production of nitrogen-free syngas (H2 + CO) from CO2 and NH3

Abstract Towards the goal of carbon neutrality, future chemical production could utilize captured CO2 as a carbon source instead of fossil carbon from petroleum or natural gas. However, the production of chemicals from CO2 is highly energy-intense. The required energy could be imported to Japan in the form of hydrogen. However, the long-distance transport of molecular hydrogen is challenging. NH3 has recently emerged as the most promising molecule for long-distance hydrogen transport and storage. The use of imported NH3 as an energy vector to realize carbon recycling in the Japanese chemical industry is promising. Syngas (H2+CO) is an important intermediate in the production of chemicals and fuels from CO2. Hydrogen is required not only as a constituent of syngas, but also as a reductant of CO2. If hydrogen is imported in the form of NH3, conventionally, NH3 would be cracked to H2 and N2, the product gases and unconverted NH3 separated, and CO/syngas then be produced through the reverse water gas shift reaction (RWGS). This conventional pathway is energy-intense and requires many unit operations. Here a novel process to produce nitrogen-free syngas directly, without producing molecular H2 first and without any dedicated gas separation steps is presented. This is realized by a using a metal oxide bed material that is active for catalytic cracking of NH3, as well as able to transport oxygen through a redox reaction in a newly designed process. This leads to an inherent separation of N2. This process, referred to herein as “NH3-RWGS” has the potential to decrease costs and increase efficiency of syngas production from CO2 and NH3.

Effect of crystalline TiO2 on V2O5WO3/TiO2 as tunable low-temperature shift De-NOx catalyst

Based on the crystalline size of anatase TiO2, a series of tunable low-temperature shift V2O5-WO3/TiO2 (VW/Ti) catalysts for NH3 selective catalytic reduction (NH3-SCR) of NOx were prepared by impregnation process. These catalysts contained a loading amount of 2 wt% WO3 and either 2 or 5 wt% V2O5. The tunable low-temperature shift De-NOx performance of the VW/Ti catalysts was significantly enhanced and dramatically decreased after heat treatment of TiO2 from 100 °C to 700 °C (Ti100 ∼ Ti700). Nearly 100 % De-NOx efficiency was achieved at a gas hourly space velocity (GHSV) of 60,000 h−1. A notable shift from higher to lower temperatures was observed from V2W2/Ti100 to V2W2/Ti600; however, the activity was lost for V2W2/Ti650 to V2W2/Ti700. When the V2O5 loading increased from 2 wt% to 5 wt%, the V5W2/Ti600 showed the highest De-NOx efficiency at 225 °C, demonstrating a remarkable synergistic effect compared to the V2W2/Ti100 catalyst, which achieved maximum efficiency at 375 °C. The De-NOx performance and low-temperature shift effect of these catalysts were elucidated by considering TiO2 crystalline size, the synergistic effect between V2O5 content and TiO2, and the V4+/V5+ oxidation state of V2O5 in the catalyst. Additionally, the high crystalline TiO2-based V2W2/Ti600 catalyst prepared in this study is expected to effectively decompose NOx at low temperatures, in contrast to the low crystalline TiO2-based V2W2/Ti100 catalyst.

Encapsulation of Cu/Fe3O4 With RT‐COF‐1 for Improved Stability in Water–Gas Shift Reaction

AbstractStability is crucial for the practical application of heterogeneous catalysts, particularly in industrial processes, where catalyst deactivation often occurs due to factors such as sintering, poisoning, and active site degradation. This study investigates the effectiveness of utilizing covalent organic frameworks (COFs), specifically RT‐COF‐1, to enhance the stability of Cu/Fe3O4 catalysts in harsh water–gas shift (WGS) reaction environments. By encapsulating Cu/Fe3O4 with trace RT‐COF‐1, we aimed to preserve the structural integrity and active interfaces between the metal components during catalytic reactions. Characterization techniques, including X‐ray photoelectron spectroscopy, nitrogen sorption, and high‐angle annular dark‐field scanning transmission electron microscopy, confirmed the successful COF coating and its role in preventing particle aggregation and maintaining active site structures over extended catalytic tests. Notably, Cu/Fe3O4@COF demonstrated significantly enhanced stability during a continuous 24‐h WGS test compared to uncoated catalysts, which exhibited rapid deactivation. Mechanistic insights indicated that COF coating reduced the number of active sites while preserving the overall morphology of the catalyst, contributing to its robust performance. Ultimately, this work highlights the potential of COF encapsulation as an effective strategy for enhancing the durability and efficacy of multifunctional catalysts in challenging reaction conditions.

Hydrogenation of CO2 to light olefins over Ga2O3-ZIF-8 tandem catalyst

Tandem catalysts composed of metal oxides and zeolites have demonstrated significant potential for the hydrogenation of CO2 to light olefins. However, their development is hindered by the competing reverse water–gas shift reaction and carbon accumulation on the zeolite surface. To address these challenges, we developed a series of innovative tandem catalysts by substituting conventional zeolites with ZIF-8. Our research primarily focused on examining the effects of metal species and content, as well as the particle size of ZIF-8, on catalytic performance. Notably, we achieved a CO2 conversion of 20.2 % and a light olefins selectivity of 73.6 % using a catalyst with 20 % Ga2O3 content and a ZIF-8 particle size of 100 nm at a reaction temperature of 340 °C and pressure of 3.0 MPa. In order to improve the stability of the catalyst, ZIF-8 was modified with La to improve its thermal stability. A CO2 conversion of 23.5 % and a light olefins selectivity of 66.5 % were maintained after 50 h of continuous reaction. While the catalytic activity of La-modified catalysts is slightly lower than that of unmodified ones, their superior stability makes them more suitable for thermal catalytic hydrogenation of CO2. Various characterizations and theoretical calculations revealed that La modification not only enhanced the thermal stability of catalyst but also improved its adsorption and activation capabilities for the reacting gases. Furthermore, the reaction mechanism of CO2 hydrogenation to light olefins was investigated by in-situ diffuse reflectance Fourier transform infrared spectroscopy. This study provides a technical foundation for designing efficient catalysts based on metal–organic frameworks in the field of carbon dioxide thermal catalytic conversion.

Decoding the Promotional Effect of Iron in Bimetallic Pt-Fe-nanoparticles on the Low Temperature Reverse Water-Gas Shift Reaction.

The reverse water-gas shift (RWGS) reaction is a key technology of the chemical industry, central to the emerging circular carbon economy. Pt-based catalysts have previously been shown to effectively promote RWGS, especially when modified by promoter elements. However, their active states are still poorly understood. Here, we show that the intimate incorporation of an iron promoter into metal-oxide-supported Pt-based nanoparticles can increase their activity and selectivity for the low temperature reverse water-gas shift (LT-RWGS) substantially and drastically outperform unpromoted Pt-based materials. Specifically, the study explores the promotional effect of iron in Pt-Fe bimetallic systems supported on silica (PtxFey@SiO2) prepared by surface organometallic chemistry (SOMC). The most active catalyst (Pt1Fe1@SiO2) shows high selectivity (>99% CO) toward CO at a formation rate of 0.192 molCO h-1 gcat-1, which is significantly higher than that of monometallic Pt@SiO2 (96% sel. and 0.022 molCO h-1 gcat-1). In-situ diffuse reflectance FT-IR spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS) indicate a dynamic process at the catalyst surface under the reaction conditions, revealing distinct reaction pathways for the monometallic Pt@SiO2 and bimetallic PtxFey@SiO2 systems.

Hydroxylated TiO2-induced high-density Ni clusters for breaking the activity-selectivity trade-off of CO2 hydrogenation

The reverse water gas shift reaction can be considered as a promising route to mitigate global warming by converting CO2 into syngas in a large scale, while it is still challenging for non-Cu-based catalysts to break the trade-off between activity and selectivity. Here, the relatively high loading of Ni species is highly dispersed on hydroxylated TiO2 through the strong Ni and −OH interactions, thereby inducing the formation of rich and stable Ni clusters (~1 nm) on anatase TiO2 during the reverse water gas shift reaction. This Ni cluster/TiO2 catalyst shows a simultaneous high CO2 conversion and high CO selectivity. Comprehensive characterizations and theoretical calculations demonstrate Ni cluster/TiO2 interfacial sites with strong CO2 activation capacity and weak CO adsorption are responsible for its unique catalytic performances. This work disentangles the activity-selectivity trade-off of the reverse water gas shift reaction, and emphasizes the importance of metal−OH interactions on surface.

Catalytic Reactivity Assessment of AgM and CuM (M = Cr, Fe) Catalysts for Dry Reforming of Methane Process with CO2.

CuM and AgM (M = Cr, Fe) catalysts were synthesized, characterized, and evaluated in methane reforming with CO2 with and without pretreatment under a H2 atmosphere. Their textural and structural characteristics were evaluated using various physicochemical methods, including XRD, B.E.T., SEM-EDS, XPS, and H2-TPR. It was shown that the nature of the species has a significant effect on these structural, textural, and reactivity properties. AgCr catalysts, presenting several oxidation states (Ag0, Ag+1, Cr3+, and Cr6+ in Ag, AgCrO2, and AgCr2O4), showed the most interesting catalytic performance in their composition. The intermediate Cr2O3 phase, formed during the catalytic reaction, played an important role as a catalytic precursor in the in situ production of highly dispersed nanoparticles, being less prone to coke formation in spite of the severe reaction conditions. In contrast, the AgFe catalyst showed low activity and a low selectivity for DRM in the explored temperature range, due to a significant contribution of the reverse water-gas shift reaction, which accounted for the low H2/CO ratios.

Formation path and kinetics of caking components from modified lignite in subcritical H2O–CO system

ABSTRACT Modification reaction of lignite in subcritical H2O–CO system can significantly increase its caking index to more than 90. Separating and extracting the caking components from modified lignite, exploring the formation path of caking components, and establishing a kinetic model for the generation of these components are of significant importance for lignite hydrogenation reaction control. The lignite modified reaction was carried out in subcritical D2O–CO systems using the isotope tracer method. The formation path of caking components was defined by solvent extraction–IRMS–GPC combination technology. The results show that the soluble substances of tetrahydrofuran (TS) and benzene (BS) are the main caking components causing the structural transformation of lignite (A). The separation of n-hexane soluble (NS) also has an effect on the caking index of the modified coal. In the hydrogenation caking component formation stage, the lignite pyrolysis fragments combine with active hydrogen generated by water gas shift reaction to form caking substances, that is, A → TS + BS + NS. The formation activation energy of caking components is in the range of 0.39–58.24 kJ/mol. In the polycondensation caking component conversion stage, three soluble substances are converted in the order of TS → BS → NS, and the activation energy for the formation of caking components is 31.710–57.616 kJ/mol.

Reactive Surface Explored by NAP-XPS: Why Ionic Conductors Are Promoters for Water Gas Shift Reaction

Reactive Surface Explored by NAP-XPS: Why Ionic Conductors Are Promoters for Water Gas Shift Reaction

Targeting carbon-neutral waste reduction: Novel process design, modelling and optimization for converting medical waste into hydrogen

This study proposes a novel system designed to turn waste masks (WM) into hydrogen while aiming at carbon neutrality. The system utilizes plasma gasification to primarily convert WM into syngas, which is subsequently upgraded through water gas shift to enhance hydrogen fraction. To mitigate carbon emissions, carbon capture techniques including monoethanolamine-based carbon absorption and oxy-fuel combustion are incorporated into the system. A high-fidelity model of the designed process is developed in Aspen Plus. Machine learning-driven optimization is applied to identify the optimal operating conditions. Utilizing Gaussian process regression-based surrogate optimization, the system achieves around 0.5 kg CO2 eq/kg H2 of levelized emissions per unit hydrogen (LEH) in the reaction stage and the execution time required for optimization is only 4 s, outperforming detailed process models-based optimization. Energy assessment highlights plasma gasification and CO2 absorption as the primary sources of energy loss. Furthermore, life cycle analysis indicates that CO2 absorption is the primary contributor to carbon emissions, accounting for approximately 60% of the total emissions. With levelized emissions of 1.27 kg CO2 eq/kg WM and 5.18 CO2 eq/kg H2, the designed system demonstrates superiority over conventional medical waste treatment and hydrogen production methods.

Reverse water-gas shift in a novel spark-coupled dielectric barrier discharge plasma: Effects of electrode structure and gas parameters

The reverse water–gas shift (RWGS) reaction holds promise for producing raw materials used in the synthesis of high-value chemicals. However, the reaction is often hindered by low CO2 conversion rates at atmospheric pressure and low temperatures. To overcome this limitation, this study developed a novel reactor based on strengthened spark-coupled dielectric barrier discharge (SSCDBD) without a catalyst, leveraging local high temperatures to enhance performance. The effects of reactor structure and gas parameters on conversion rate and energy efficiency were systematically investigated. The results indicated that the SSCDBD device notably improved CO2 conversion compared to conventional plasma techniques, such as dielectric barrier discharge (DBD), spark discharge, and spark-coupled dielectric barrier discharge (SCDBD), with respective increases of 1000 %, 12.65 %, and 2.79 %. Notably, varying the length of the auxiliary electrode affects the capacitance of the equivalent capacitor and, consequently, the discharge intensity. Furthermore, Increasing the electrode length from 4 cm to 20 cm improved the CO2 conversion rate from 43.7 % to 59.8 %. Moreover, CO2 conversion was positively correlated with the discharge distance, which also affected the volume of the electric arc. However, distances exceeding 1.2 cm interfered with arc formation. At a CO2:H2 molar ratio of 1:1, with an auxiliary electrode length of 12 cm and a discharge distance of 0.8 cm, the maximum CO2 conversion rate of 66 % was achieved at a total feed flow rate of 100 mL min−1, while maintaining a CO selectivity higher than 99 %. Additionally, with a total feed flow rate of 400 mL min−1, CO2 conversion reached 29 % and energy efficiency peaked at 6.34 %.