Progress on the Electrochemical Reduction of CO₂ to Syngas Using Non-Precious Metal Catalysts

Abstract

Converting CO₂ into usable energy through electrocatalytic CO₂ reduction is a meaningful strategy due to its tunable and high selectivity and mild reaction conditions. This paper reviews recent progress in electrocatalytic CO₂-to-syngas conversion via non-precious metal catalysts. Non-precious metal-based materials have the advantages of lower cost, richer raw materials, and broader industrial prospects compared to precious metal materials. Although in most cases the electrocatalytic performance of non-precious metal materials is lower than that of precious metal materials, four typical catalyst design strategies—carbon substrate loading, morphological structure control, elemental doping, and alloy/composite design strategies—were summarized to boost their performance in converting CO₂ into syngas. The review also summarizes the current challenges and future directions of catalyst design, aiming to provide new insights into designing advanced non-precious metal materials for effective CO₂ to syngas conversion in the future. In addition, the impacts of equipment such as reactors and electrolytes on the overall catalytic performance have been summarized in this review, aiming to promote CO₂ conversion efficiency by combining catalyst design and catalytic equipment design and guide practice. This review presents a comprehensive overview of the latest advances in electrocatalytic CO₂ to syngas conversion, focusing on non-precious metal catalysts. It systematically dissects key design strategies—carbon support loading, morphology and structure control, elemental doping, and alloy and metal composite—and evaluates their impacts on activity, selectivity, and stability.

Keywords

catalyst design strategies / electrocatalytic CO₂ reduction / non-precious metal catalysts / syngas production

References

[1] T. A. Jacobson, J. S. Kler, M. T. Hernke, R. K. Braun, K. C. Meyer, and W. E. Funk, “Direct Human Health Risks of Increased Atmospheric Carbon Dioxide,” Nature Sustainability 2, no. 8 (2019): 691–701.

[2] U. Murthy, M. S. Shaari, P. A. Mariadas, and N. Z. Abidin, “The Relationships Between CO₂ Emissions, Economic Growth and Life Expectancy,” Journal of Asian Finance, Economics and Business 8, no. 4 (2021): 801–808.

[3] C. Chen, J. F. Khosrowabadi Kotyk, and S. W. Sheehan, “Progress Toward Commercial Application of Electrochemical Carbon Dioxide Reduction,” Chem 4, no. 10 (2018): 2571–2586.

[4] M. Jiang, M. Zhu, M. Wang, et al., “Review on Electrocatalytic Coreduction of Carbon Dioxide and Nitrogenous Species for Urea Synthesis,” ACS Nano 17, no. 4 (2023): 3209–3224.

[5] L. Peng, Y. Zhang, R. He, N. Xu, and J. Qiao, “Research Advances in Electrocatalysts, Electrolytes, Reactors and Membranes for the Electrocatalytic Carbon Dioxide Reduction Reaction,” Acta Physico Chimica Sinica 39, no. 12 (2023): 2302037.

[6] R. M. Arán-Ais, D. Gao, and B. Roldan Cuenya, “Structure- and Electrolyte-Sensitivity in CO₂ Electroreduction,” Accounts of Chemical Research 51, no. 11 (2018): 2906–2917.

[7] F.-Y. Gao, R.-C. Bao, M.-R. Gao, and S.-H. Yu, “Electrochemical CO₂-to-CO Conversion: Electrocatalysts, Electrolytes, and Electrolyzers,” Journal of Materials Chemistry A 8, no. 30 (2020): 15458–15478.

[8] F. Bellato, M. Ferri, D. Zhu, et al., “Indium Arsenide Quantum Dot Derived Catalyst for Selective CO₂ Electrochemical Reduction to Formate,” ACS Energy Letters 9, no. 4 (2024): 1097–1102.

[9] M. Jiang, M. Zhu, H. Wang, et al., “Rapid and Green Electric-Explosion Preparation of Spherical Indium Nanocrystals With Abundant Metal Defects for Highly-Selective CO₂ Electroreduction,” Nano Letters 23, no. 1 (2023): 291–297.

[10] S. Xue, X. Liang, Q. Zhang, et al., “Density Functional Theory Study of CuAg Bimetal Electrocatalyst for CO₂RR to Produce CH₃OH,” Catalysts 14, no. 1 (2024): 7.

[11] Y. J. Tak, J. A. Kwon, D. Y. Shin, A. Soon, and D.-H. Lim, “Alternative Cu₃Zn Catalysts for Enhanced Reduction of CO₂ to CH₄: A Density Functional Theory-Based Approach,” Surfaces and Interfaces 31 (2022): 102030.

[12] G. Wang, J. Chen, Y. Ding, et al., “Electrocatalysis for CO₂ Conversion: From Fundamentals to Value-Added Products,” Chemical Society Reviews 50, no. 8 (2021): 4993–5061.

[13] C. Wang, Z. Sun, Y. Zheng, and Y. H. Hu, “Recent Progress in Visible Light Photocatalytic Conversion of Carbon Dioxide,” Journal of Materials Chemistry A 7, no. 3 (2019): 865–887.

[14] S. Jin, Z. Hao, K. Zhang, Z. Yan, and J. Chen, “Advances and Challenges for the Electrochemical Reduction of CO₂ to CO: From Fundamentals to Industrialization,” Angewandte Chemie International Edition 60, no. 38 (2021): 20627–20648.

[15] H. Zhang, Y. Qiao, Y. Wang, Y. Zheng, and H. Huang, “In Situ Oxidative Etching-Enabled Synthesis of Hollow Cu₂O Nanocrystals for Efficient CO₂RR Into C₂₊ Products,” Sustainable Energy & Fuels 6, no. 20 (2022): 4860–4865.

[16] S. Cui, S. Li, R. Deng, et al., “Progress in Cu-Based Electrocatalysts for Electrochemical CO₂ Reduction to C₂₊ Products,” Catalysis Science & Technology 14, no. 10 (2024): 2697–2716.

[17] J.-W. DuanMu, F.-Y. Gao, and M.-R. Gao, “A Critical Review of Operating Stability Issues in Electrochemical CO₂ Reduction,” Science China Materials 67, no. 6 (2024): 1721–1739.

[18] M. B. Ross, Y. Li, P. De Luna, D. Kim, E. H. Sargent, and P. Yang, “Electrocatalytic Rate Alignment Enhances Syngas Generation,” Joule 3 (2019): 257–264.

[19] Y. Hua, J. Wang, T. Min, and Z. Gao, “Electrochemical CO₂ Conversion Towards Syngas: Recent Catalysts and Improving Strategies for Ratio-Tunable Syngas,” Journal of Power Sources 535 (2022): 231453.

[20] S. Han, D. Fan, N. Chen, et al., “Efficient Conversion of Syngas Into Ethanol by Tandem Catalysis,” ACS Catalysis 13, no. 16 (2023): 10651–10660.

[21] I. V. Yentekakis, P. Panagiotopoulou, and G. Artemakis, “A Review of Recent Efforts to Promote Dry Reforming of Methane (DRM) to Syngas Production via Bimetallic Catalyst Formulations,” Applied Catalysis, B: Environmental 296 (2021): 120210.

[22] F. Jiao, J. Li, X. Pan, et al., “Selective Conversion of Syngas to Light Olefins,” Science 351 (2016): 1065–1068.

[23] X. Han, J. Zuo, D. Wen, and Y. Yuan, “Toluene Methylation With Syngas to Para-Xylene by Bifunctional ZnZrO -HZSM-5 Catalysts,” Chinese Journal of Catalysis 43, no. 4 (2022): 1156–1164.

[24] Y. Ni, K. Wang, W. Zhu, and Z. Liu, “Realizing High Conversion of Syngas to Gasoline-Range Liquid Hydrocarbons on a Dual-Bed-Mode Catalyst,” Chem Catalysis 1, no. 2 (2021): 383–392.

[25] B. Chang, Z. Min, N. Liu, et al., “Electrocatalytic CO₂ Reduction to Syngas,” Green Energy & Environment 9, no. 7 (2024): 1085–1100.

[26] F. Jiao, B. Bai, G. Li, et al., “Disentangling the Activity-Selectivity Trade-Off in Catalytic Conversion of Syngas to Light Olefins,” Science 380, no. 6647 (2023): 727–730.

[27] M. Fiore, V. Magi, and A. Viggiano, “Internal Combustion Engines Powered by Syngas: A Review,” Applied Energy 276 (2020): 115415.

[28] E. V. Jithin, G. K. S. Raghuram, T. V. Keshavamurthy, R. K. Velamati, C. Prathap, and R. J. Varghese, “A Review on Fundamental Combustion Characteristics of Syngas Mixtures and Feasibility in Combustion Devices,” Renewable and Sustainable Energy Reviews 146 (2021): 111178.

[29] Y. Wang, J. Guo, L. Qu, P. Webley, H. Ding, and G. K. Li, “Syngas Production From the Air,” Chem Catalysis 5, no. 3 (2025): 101254.

[30] V. Dieterich, A. Buttler, A. Hanel, H. Spliethoff, and S. Fendt, “Power-to-Liquid via Synthesis of Methanol, DME or Fischer–Tropsch-Fuels: A Review,” Energy & Environmental Science 13, no. 10 (2020): 3207–3252.

[31] Z. Ge, L. Guo, and H. Jin, “Hydrogen Production by Non-Catalytic Partial Oxidation of Coal in Supercritical Water: The Study on Reaction Kinetics,” International Journal of Hydrogen Energy 42, no. 15 (2017): 9660–9666.

[32] M. Faraji and M. Saidi, “Hydrogen-Rich Syngas Production via Integrated Configuration of Pyrolysis and Air Gasification Processes of Various Algal Biomass: Process Simulation and Evaluation Using Aspen Plus Software,” International Journal of Hydrogen Energy 46, no. 35 (2021): 18844–18856.

[33] N. Zhao, K. Zhao, H. Zhang, J. Sheng, S. Feng, and W. Wang, “A 3D Printed, Metal-Free, Carbon-Based Catalytic Electrode for Converting CO₂ Into Syngas,” Green Chemistry 27, no. 14 (2025): 3646–3654.

[34] Y. Hori, A. Murata, and R. Takahashi, “Formation of Hydrocarbons in the Electrochemical Reduction of Carbon Dioxide at a Copper Electrode in Aqueous Solution,” Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases 85, no. 8 (1989): 2309–2326.

[35] Y. Hori, H. Wakebe, T. Tsukamoto, and O. Koga, “Electrocatalytic Process of CO Selectivity in Electrochemical Reduction of CO₂ at Metal Electrodes in Aqueous Media,” Electrochimica Acta 39, no. 11–12 (1994): 1833–1839.

[36] B. M. Tackett, J. H. Lee, and J. G. Chen, “Electrochemical Conversion of CO₂ to Syngas With Palladium-Based Electrocatalysts,” Accounts of Chemical Research 53, no. 8 (2020): 1535–1544.

[37] F. Pan, B. Li, E. Sarnello, et al., “Atomically Dispersed Iron–Nitrogen Sites on Hierarchically Mesoporous Carbon Nanotube and Graphene Nanoribbon Networks for CO₂ Reduction,” ACS Nano 14, no. 5 (2020): 5506–5516.

[38] J. Guo, J. Huo, Y. Liu, et al., “Nitrogen-Doped Porous Carbon Supported Nonprecious Metal Single-Atom Electrocatalysts: From Synthesis to Application,” Small Methods 3, no. 10 (2019): 1900159.

[39] S. Lv, X. Sun, B. Wang, et al., “An Innovative Approach to Precisely Tailor the Composition of Syngas in CO₂ Electroreduction,” Advanced Science 12, no. 35 (2025): e05424.

[40] H. Ooka, J. Huang, and K. S. Exner, “The Sabatier Principle in Electrocatalysis: Basics, Limitations, and Extensions,” Frontiers in Energy Research 9 (2021): 654460.

[41] J. T. Feaster, C. Shi, E. R. Cave, et al., “Understanding Selectivity for the Electrochemical Reduction of Carbon Dioxide to Formic Acid and Carbon Monoxide on Metal Electrodes,” ACS Catalysis 7, no. 7 (2017): 4822–4827.

[42] S. Li, L. Fu, Z. Qu, M. Qin, and L. Zhou, “Ga₂O₃/ZnO Dual-Site Catalyst for Efficient Electrocatalytic CO₂ Reduction to Produce Tunable Syngas,” Applied Surface Science 709 (2025): 163877.

[43] W. Zhang, J. Wang, T. Ouyang, et al., “Efficient CO₂ Electroreduction to CO on Chiral Nanostructured Au Films,” ACS Catalysis 15, no. 14 (2025): 12377–12385.

[44] J.-H. Kim, H. Woo, S.-W. Yun, et al., “Highly Active and Selective Au Thin Layer on Cu Polycrystalline Surface Prepared by Galvanic Displacement for the Electrochemical Reduction of CO₂ to CO,” Applied Catalysis, B: Environmental 213 (2017): 211–215.

[45] L. Mascaretti, A. Niorettini, B. R. Bricchi, et al., “Syngas Evolution From CO₂ Electroreduction by Porous Au Nanostructures,” ACS Applied Energy Materials 3, no. 5 (2020): 4658–4668.

[46] Q. Yu, “Theoretical Studies of Non-Noble Metal Single-Atom Catalyst Ni₁/MoS₂: Electronic Structure and Electrocatalytic CO₂ Reduction,” Science China Materials 66, no. 3 (2023): 1079–1088.

[47] W. Yang, J.-H. Zhang, R. Si, L.-M. Cao, D.-C. Zhong, and T.-B. Lu, “Efficient and Steady Production of 1:2 Syngas (CO/H₂) by Simultaneous Electrochemical Reduction of CO₂ and H₂O,” Inorganic Chemistry Frontiers 8, no. 7 (2021): 1695–1701.

[48] S.-F. Hung, A. Xu, X. Wang, et al., “A Metal-Supported Single-Atom Catalytic Site Enables Carbon Dioxide Hydrogenation,” Nature Communications 13, no. 1 (2022): 819.

[49] R. Zhang, X. Kong, R. Ren, et al., “Recent Advances in Copper-Based Catalysts for Electrochemical Carbon Dioxide Reduction to C₂₊ Products,” Carbon Neutralization 4, no. 5 (2025): e70041.

[50] C. Wang, X. Hu, X. Hu, et al., “Typical Transition Metal Single-Atom Catalysts With a Metal-Pyridine N Structure for Efficient CO₂ Electroreduction,” Applied Catalysis, B: Environmental 296 (2021): 120331.

[51] C. Wang, Y. Liu, H. Ren, Q. Guan, S. Chou, and W. Li, “Diminishing the Uncoordinated N Species in Co–N–C Catalysts Toward Highly Efficient Electrochemical CO₂ Reduction,” ACS Catalysis 12, no. 4 (2022): 2513–2521.

[52] R. Daiyan, R. Chen, P. Kumar, et al., “Tunable Syngas Production Through CO₂ Electroreduction on Cobalt–Carbon Composite Electrocatalyst,” ACS Applied Materials & Interfaces 12, no. 8 (2020): 9307–9315.

[53] K. Jiang, S. Siahrostami, T. Zheng, et al., “Isolated Ni Single Atoms in Graphene Nanosheets for High-Performance CO₂ Reduction,” Energy & Environmental Science 11, no. 4 (2018): 893–903.

[54] R. Daiyan, X. Zhu, Z. Tong, et al., “Transforming Active Sites in Nickel–Nitrogen–Carbon Catalysts for Efficient Electrochemical CO₂ Reduction to CO,” Nano Energy 78 (2020): 105213.

[55] H.-B. Yang, S.-F. Hung, S. Liu, et al., “Atomically Dispersed Ni(I) as the Active Site for Electrochemical CO₂ Reduction,” Nature Energy 3, no. 2 (2018): 140–147.

[56] M. S. Kim, A. Priyadarsini, J.-H. Lee, et al., “Ligand Environment Engineering of Nickel Single Atomic Sites for Efficient Electrochemical Carbon Dioxide Reduction Reaction,” Journal of Materials Chemistry A 13, no. 7 (2025): 3834–3848.

[57] X. Wang, Z. Chen, X. Zhao, et al., “Regulation of Coordination Number Over Single Co Sites: Triggering the Efficient Electroreduction of CO₂,” Angewandte Chemie International Edition 57, no. 7 (2018): 1944–1948.

[58] W. Zhu, J. Fu, J. Liu, et al., “Tuning Single Atom–Nanoparticle Ratios of Ni-Based Catalysts for Synthesis Gas Production From CO₂,” Applied Catalysis, B: Environmental 264 (2020): 118502.

[59] X. Li, S. Xi, L. Sun, et al., “Isolated FeN₄ Sites for Efficient Electrocatalytic CO₂ Reduction,” Advanced Science 7, no. 7 (2020): 2001545.

[60] L. Wang, X. Lai, Y. Xu, et al., “Fabricating Penta-Coordinated Fe Single Atoms for Electrochemical CO₂ Reduction to Syngas,” Catalysis Science & Technology 13, no. 13 (2023): 3946–3952.

[61] Y. Hua, B. Zhang, W. Hao, and Z. Gao, “Boosting CO Desorption on Dual Active Site Electrocatalysts for CO₂ Reduction to Produce Tunable Syngas,” Cell Reports Physical Science 3, no. 2 (2022): 100703.

[62] H. Zhang, J. Li, S. Xi, et al., “A Graphene-Supported Single-Atom FeN₅ Catalytic Site for Efficient Electrochemical CO₂ Reduction,” Angewandte Chemie International Edition 58, no. 42 (2019): 14871–14876.

[63] T. N. Huan, N. Ranjbar, G. Rousse, et al., “Electrochemical Reduction of CO₂ Catalyzed by Fe–N–C Materials: A Structure–Selectivity Study,” ACS Catalysis 7, no. 3 (2017): 1520–1525.

[64] Q. He, D. Liu, J. H. Lee, et al., “Electrochemical Conversion of CO₂ to Syngas With Controllable CO/H₂ Ratios Over Co and Ni Single-Atom Catalysts,” Angewandte Chemie International Edition 59, no. 8 (2020): 3033–3037.

[65] Y. Chen, M. Xia, C. Zhou, et al., “Hierarchical Dual Single-Atom Catalysts With Coupled CoN₄ and NiN₄ Moieties for Industrial-Level CO₂ Electroreduction to Syngas,” ACS Nano 17, no. 22 (2023): 22095–22105.

[66] W. Ni, Z. Liu, X. Guo, et al., “Dual Single-Cobalt Atom-Based Carbon Electrocatalysts for Efficient CO₂-to-Syngas Conversion With Industrial Current Densities,” Applied Catalysis, B: Environmental 291 (2021): 120092.

[67] M. Qi, M. J. Zachman, Y. Li, et al., “Highly Dense Atomic Fe–Ni Dual Metal Sites for Efficient CO₂ to CO Electrolyzers at Industrial Current Densities,” Energy & Environmental Science 18, no. 11 (2025): 5643–5656.

[68] L. Meng, E. Zhang, H. Peng, et al., “Bi/Zn Dual Single-Atom Catalysts for Electroreduction of CO₂ to Syngas,” ChemCatChem 14, no. 7 (2022): e202101801.

[69] X. Zou, C. Ma, A. Li, et al., “Nanoparticle-Assisted Ni–Co Binary Single-Atom Catalysts Supported on Carbon Nanotubes for Efficient Electroreduction of CO₂ to Syngas With Controllable CO/H₂ Ratios,” ACS Applied Energy Materials 4, no. 9 (2021): 9572–9581.

[70] R. Yun, B. Zhang, F. Zhan, Z. Xin, T. Sheng, and Z. Shi, “Electrocatalysis CO₂ to Tunable Syngas Upon Fe Clusters Catalyst Dispersed on Bamboo-Like NCTs,” Inorganic Chemistry 61, no. 24 (2022): 9375–9380.

[71] F. Zhao, C. Zhang, M. Guo, et al., “CO₂ Hydrogenation to Methanol Over Ni/In₂O₃: Effects of In₂O₃ Morphology,” ACS Catalysis 15, no. 21 (2025): 18404–18415.

[72] S. A. Mahyoub, F. A. Qaraah, S. Yan, et al., “3D Cu/In Nanocones by Morphological and Interface Engineering Design in Achieving a High Current Density for Electroreduction of CO₂ to Syngas Under Elevated Pressure,” Journal of CO2 Utilization 61 (2022): 102033.

[73] C. An, Y. Shen, W. Yan, L. Dai, and C. An, “Surface-Tuning Nanoporous AuCu₃ Engineering Syngas Proportion by Electrochemical Conversion of CO₂,” Nano Research 14, no. 11 (2021): 3907–3912.

[74] B. Chang, X.-G. Zhang, Z. Min, et al., “Efficient Electrocatalytic Conversion of CO₂ to Syngas for the Fischer–Tropsch Process Using a Partially Reduced Cu₃P Nanowire,” Journal of Materials Chemistry A 9, no. 33 (2021): 17876–17884.

[75] B. Qin, Q. Zhang, Y.-H. Li, G. Yang, and F. Peng, “Formation of Lattice-Dislocated Zinc Oxide via Anodic Corrosion for Electrocatalytic CO₂ Reduction to Syngas With a Potential-Dependent CO:H₂ Ratio,” ACS Applied Materials & Interfaces 12, no. 27 (2020): 30466–30473.

[76] P. Chen, Y. Jiao, Y.-H. Zhu, et al., “Syngas Production From Electrocatalytic CO₂ Reduction With High Energetic Efficiency and Current Density,” Journal of Materials Chemistry A 7, no. 13 (2019): 7675–7682.

[77] B. Qin, Y. Li, H. Fu, et al., “Electrochemical Reduction of CO₂ Into Tunable Syngas Production by Regulating the Crystal Facets of Earth-Abundant Zn Catalyst,” ACS Applied Materials & Interfaces 10, no. 24 (2018): 20530–20539.

[78] B. Xiong, Y. Yang, J. Liu, J. Ding, and Y. Yang, “Electrochemical Conversion of CO₂ to Syngas Over Cu-M (M = Cd, Zn, Ni, Ag, and Pd) Bimetal Catalysts,” Fuel 304 (2021): 121341.

[79] X. Bai, J. Ge, H. Yang, et al., “Building of Rich (111) Grain Boundary in Copper for Syngas in Electrochemical CO₂ Reduction,” Applied Catalysis B: Environment and Energy 356 (2024): 124212.

[80] D. Yang, Q. Zhu, X. Sun, et al., “Electrosynthesis of a Defective Indium Selenide With 3D Structure on a Substrate for Tunable CO₂ Electroreduction to Syngas,” Angewandte Chemie International Edition 59, no. 6 (2020): 2354–2359.

[81] K. Han, P. Ngene, and P. de Jongh, “Structure Dependent Product Selectivity for CO₂ Electroreduction on ZnO Derived Catalysts,” ChemCatChem 13, no. 8 (2021): 1998–2004.

[82] Y. Han, G. Fan, Y. Guo, et al., “Plasma-Driven Efficient Conversion of CO₂ and H₂O Into Pure Syngas With Controllable Wide H₂/CO Ratios Over Metal–Organic Frameworks Featuring In Situ Evolved Ligand Defects,” Angewandte Chemie International Edition 63, no. 15 (2024): e202406007.

[83] X. Wang, J. Lv, J. Zhang, et al., “Hierarchical Heterostructure of SnO₂ Confined on Cus Nanosheets for Efficient Electrocatalytic CO₂ Reduction,” Nanoscale 12, no. 2 (2020): 772–784.

[84] X. Ma, F. Wang, D. Jiao, et al., “Room-Temperature Liquid Metal Synthesis of Nanoporous Copper-Indium Heterostructures for Efficient Carbon Dioxide Reduction to Syngas,” Science China Materials 65, no. 12 (2022): 3504–3512.

[85] K. Li, J. Sun, S. Liu, et al., “Tuning Sb Atoms on Cu-Based Catalysts for Electrochemical Conversion of CO₂ to Syngas,” ChemCatChem 17, no. 3 (2025): e202401406.

[86] H. Xie, S. Chen, F. Ma, et al., “Boosting Tunable Syngas Formation via Electrochemical CO₂ Reduction on Cu/In₂O₃ Core/Shell Nanoparticles,” ACS Applied Materials & Interfaces 10, no. 43 (2018): 36996–37004.

[87] J. Wang, Q. Xiang, W. Zhang, et al., “Effectively Tuning the Ratio of CO and H₂ into Syngas Through CO₂ Electrochemical Reduction Over a Wide Potential Range on a ZnO Nanosheet via Ni Doping,” ACS Applied Energy Materials 5, no. 5 (2022): 5531–5539.

[88] R. He, A. Zhang, Y. Ding, et al., “Achieving the Widest Range of Syngas Proportions at High Current Density over Cadmium Sulfoselenide Nanorods in CO₂ Electroreduction,” Advanced Materials 30, no. 28 (2018): 1705872.

[89] T. Chen, T. Liu, T. Ding, et al., “Surface Oxygen Injection in Tin Disulfide Nanosheets for Efficient CO₂ Electroreduction to Formate and Syngas,” Nano-Micro Letters 13, no. 1 (2021): 189.

[90] P.-P. Guo, Z.-H. He, H.-H. Cao, et al., “Efficient Synthesis of Syngas From CO₂ Electrochemical Reduction Over a Dual Functional FexC@CNT/N-MXene Catalyst,” Applied Catalysis B: Environment and Energy 347 (2024): 123786.

[91] L. Guan, H. Fu, Y. Wang, J. Wang, N. Zhang, and T. Liu, “Electrochemical Reduction of CO₂ Into Syngas by N-Modified NiSb Nanowires,” Inorganic Chemistry 63, no. 40 (2024): 15821–15828.

[92] J. Zhao, J. Deng, J. Han, S. Imhanria, K. Chen, and W. Wang, “Effective Tunable Syngas Generation via CO₂ Reduction Reaction by Non-Precious Fe–N–C Electrocatalyst,” Chemical Engineering Journal 389 (2020): 124323.

[93] F. Proietto, S. Li, A. Loria, et al., “High-Pressure Synthesis of CO and Syngas From CO₂ Reduction Using Ni-N-Doped Porous Carbon Electrocatalyst,” Chemical Engineering Journal 429 (2022): 132251.

[94] J. Liu, J. Zhao, X. Deng, Y. Sun, S. Imhanria, and W. Wang, “Sn and N Co-Doped Porous Carbon Catalyst Electrochemically Reduce CO₂ Into Tunable Syngas,” Journal of the Taiwan Institute of Chemical Engineers 121 (2021): 122–127.

[95] G. An, K. Wang, M. Yang, et al., “Rational Design of Metal-Free Nitrogen-Doped Carbon for Controllable Reduction of CO₂ to Syngas,” Molecules 30, no. 4 (2025): 953.

[96] L. Delafontaine, T. Asset, and P. Atanassov, “Metal–Nitrogen–Carbon Electrocatalysts for CO₂ Reduction Towards Syngas Generation,” Chemsuschem 13, no. 7 (2020): 1688–1698.

[97] J. Bo, M. Li, X. Zhu, Q. Ge, J. Han, and H. Wang, “Bamboo-Like N-Doped Carbon Nanotubes Encapsulating M(Co, Fe)-Ni Alloy for Electrochemical Production of Syngas With Potential-Independent CO/H₂ Ratios,” Frontiers of Chemical Science and Engineering 16, no. 4 (2022): 498–510.

[98] C. Ma, X. Zou, A. Li, et al., “Rapid Flame Synthesis of Carbon Doped Defective ZnO for Electrocatalytic CO₂ Reduction to Syngas,” Electrochimica Acta 411 (2022): 140098.

[99] Y. Wang, R. Xie, N. Ci, et al., “Modified Cu Active Sites by Alloying for Efficient Electrocatalytic Reduction CO₂ to CO,” Journal of Energy Chemistry 99 (2024): 450–457.

[100] J. Leverett, M. H. A. Khan, T. Tran-Phu, et al., “Renewable Power for Electrocatalytic Generation of Syngas: Tuning the Syngas Ratio by Manipulating the Active Sites and System Design,” ChemCatChem 14, no. 19 (2022): e202200981.

[101] S. Shahrestani, M. Beheshti, and S. Kakooei, “Investigation of Electrochemical Parameters on Cost-Effective Zn/Ni-Based Electrocatalysts for Electrochemical CO₂ Reduction Reaction to Syngas (H₂+CO),” Journal of the Electrochemical Society 169, no. 4 (2022): 044519.

[102] T. Liu, H. Luo, T. Ouyang, and Z.-Q. Liu, “In Situ Exsolved CuZn Alloy Electrocatalysts for CO₂ Conversion to Tunable Syngas Production,” Advanced Functional Materials 35, no. 5 (2025): 2415367.

[103] Y. Guo, Y. Luo, H. Wang, et al., “Mediating Zn Loading on Cu-Zn Bimetallic Catalyst for Electrochemical CO₂ Reduction Into Tunable Syngas,” Fuel 392 (2025): 134821.

[104] Z. Liang, L. Song, M. Sun, B. Huang, and Y. Du, “Tunable CO/H₂ Ratios of Electrochemical Reduction of CO₂ Through the Zn-Ln Dual Atomic Catalysts,” Science Advances 7, no. 50 (2021): eabl4915.

[105] R. Zhang, J. Zhang, Y. Song, et al., “Cu₂O Nano-Homojunction for High-Efficiency Electrocatalytic CO₂-to-Ethylene Conversion,” Angewandte Chemie International Edition 64, no. 31 (2025): e202501554.

[106] S. Wang, W. Peng, H. Ma, et al., “Theory-Guided Modification of Ionic Liquid on Cu₂O Promotes Asymmetric C–C Coupling for CO₂ Conversion,” ACS Catalysis 15, no. 16 (2025): 14127–14137.

[107] Y. Luo, X. Chen, X. Liu, et al., “Electrochemical CO₂ Reduction to Syngas on Copper Mesh Electrode: Alloying Strategy for Tuning Syngas Composition,” Carbon Capture Science & Technology 13 (2024): 100254.

[108] H. Liu, E. Shi, W. Guo, et al., “Selectivity Control for CO₂ Electroreduction to Syngas Using Fe/CuO_x Catalysts With High Current Density,” Chemical Communications 59, no. 74 (2023): 9746–9749.

[109] K. Malik, B. M. Rajbongshi, and A. Verma, “Syngas Production From Electrochemical Reduction of CO₂ at High Current Density Using Oxide Derived Zn/Cu Nanocomposite,” Journal of CO2 Utilization 33 (2019): 311–319.

[110] L. Dai, Q. Qin, P. Wang, et al., “Ultrastable Atomic Copper Nanosheets for Selective Electrochemical Reduction of Carbon Dioxide,” Science Advances 3, no. 9 (2017): e1701069.

[111] J. Xu, X. Li, W. Liu, et al., “Carbon Dioxide Electroreduction into Syngas Boosted by a Partially Delocalized Charge in Molybdenum Sulfide Selenide Alloy Monolayers,” Angewandte Chemie International Edition 56, no. 32 (2017): 9121–9125.

[112] N. Meng, C. Liu, Y. Liu, Y. Yu, and B. Zhang, “Efficient Electrosynthesis of Syngas With Tunable CO/H₂ Ratios Over Zn_xCd_1-xS–Amine Inorganic–Organic Hybrids,” Angewandte Chemie International Edition 58, no. 51 (2019): 18908–18912.

[113] T. Van Phuc, S. G. Kang, J. S. Chung, and S. H. Hur, “Highly CO Selective Ca and Zn Hybrid Metal-Organic Framework Electrocatalyst for the Electrochemical Reduction of CO₂,” Current Applied Physics 27 (2021): 31–37.

[114] H. Zhong, M. Ghorbani-Asl, K. H. Ly, et al., “Synergistic Electroreduction of Carbon Dioxide to Carbon Monoxide on Bimetallic Layered Conjugated Metal-Organic Frameworks,” Nature Communications 11, no. 1 (2020): 1409.

[115] Y. Liu and N. Yuan, “Flexible Control of Co/Zn-Nitrogen Coordination in ZiFs for Electrochemical CO₂ Reduction to Tunable Syngas,” Chemical Communications 60, no. 64 (2024): 13778–13781.

[116] M. H. Abouremeleh, R. A. Rivera, T. A. Kistler, and P. Agbo, “Durability Optimization of CO₂ Electrolyzers for Syngas Evolution,” Journal of the Electrochemical Society 172, no. 7 (2025): 074513.

[117] C. Chen, Y. Li, and P. Yang, “Address the ‘Alkalinity Problem’ in CO₂ Electrolysis With Catalyst Design and Translation,” Joule 5, no. 4 (2021): 737–742.

[118] M. R. Singh, E. L. Clark, and A. T. Bell, “Effects of Electrolyte, Catalyst, and Membrane Composition and Operating Conditions on the Performance of Solar-Driven Electrochemical Reduction of Carbon Dioxide,” Physical Chemistry Chemical Physics 17, no. 29 (2015): 18924–18936.

[119] D. Gao, P. Wei, H. Li, L. Lin, G. Wang, and X. Bao, “Designing Electrolyzers for Electrocatalytic CO₂ Reduction,” Acta Physico Chimica Sinica 37, no. 5 (2020): 2009021.

[120] D. M. Weekes, D. A. Salvatore, A. Reyes, A. Huang, and C. P. Berlinguette, “Electrolytic CO₂ Reduction in a Flow Cell,” Accounts of Chemical Research 51, no. 4 (2018): 910–918.

[121] E. W. Lees, B. A. W. Mowbray, F. G. L. Parlane, and C. P. Berlinguette, “Gas Diffusion Electrodes and Membranes for CO₂ Reduction Electrolysers,” Nature Reviews Materials 7, no. 1 (2022): 55–64.

[122] K. Hara and T. Sakata, “Large Current Density CO₂ Reduction Under High Pressure Using Gas Diffusion Electrodes,” Bulletin of the Chemical Society of Japan 70, no. 3 (1997): 571–576.

[123] Z.-Y. Cheng, D.-Y. Lu, J.-Y. Chen, et al., “Electrochemical CO₂ Reduction Technology Toward Practical Application: Status Quo and Challenges,” ChemistrySelect 10, no. 3 (2025): e202404576.

[124] A. A. Samu, I. Szenti, Á. Kukovecz, B. Endrődi, and C. Janáky, “Systematic Screening of Gas Diffusion Layers for High Performance CO₂ Electrolysis,” Communications Chemistry 6, no. 1 (2023): 41.

[125] C. M. Gabardo, C. P. O'Brien, J. P. Edwards, et al., “Continuous Carbon Dioxide Electroreduction to Concentrated Multi-Carbon Products Using a Membrane Electrode Assembly,” Joule 3, no. 11 (2019): 2777–2791.

[126] C.-T. Dinh, T. Burdyny, M. G. Kibria, et al., “CO₂ Electroreduction to Ethylene via Hydroxide-Mediated Copper Catalysis at an Abrupt Interface,” Science 360, no. 6390 (2018): 783–787.

[127] B. S. Crandall, B. H. Ko, S. Overa, et al., “Kilowatt-Scale Tandem CO₂ Electrolysis for Enhanced Acetate and Ethylene Production,” Nature Chemical Engineering 1, no. 5 (2024): 421–429.

[128] Z. Yao, X. He, and R. Lin, “Electrochemical Carbon Dioxide Reduction in Acidic Media,” Electrochemical Energy Reviews 7, no. 1 (2024): 8.

[129] J. Yang, J. Jiao, S. Liu, et al., “Switching Reaction Pathways of CO₂ Electroreduction by Modulating Cations in the Electrochemical Double Layer,” Angewandte Chemie International Edition 63, no. 27 (2024): e202410145.

[130] Z. Bao, Y. Li, X. Zhou, F. Gao, Q. Du, and K. Jiao, “Transport Properties of Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells: Effects of Compression,” International Journal of Heat and Mass Transfer 178 (2021): 121608.

[131] Y. Hori, H. Ito, K. Okano, K. Nagasu, and S. Sato, “Silver-Coated Ion Exchange Membrane Electrode Applied to Electrochemical Reduction of Carbon Dioxide,” Electrochimica Acta 48, no. 18 (2003): 2651–2657.

[132] X. He, L. Lin, X. Li, et al., “Roles of Copper(I) in Water-Promoted CO₂ Electrolysis to Multi-Carbon Compounds,” Nature Communications 15, no. 1 (2024): 9923.

[133] E. J. Dufek, T. E. Lister, S. G. Stone, and M. E. McIlwain, “Operation of a Pressurized System for Continuous Reduction of CO₂,” Journal of the Electrochemical Society 159, no. 9 (2012): F514–F517.

[134] D. T. Whipple, E. C. Finke, and P. J. A. Kenis, “Microfluidic Reactor for the Electrochemical Reduction of Carbon Dioxide: The Effect of pH,” Electrochemical and Solid-State Letters 13, no. 9 (2010): B109–B111.

[135] P. Yan, T. Li, and K. Li, “Micromonolithic Electrochemical Cells for Sustainable Syngas Production From H₂O and CO₂,” ACS Sustainable Chemistry & Engineering 13, no. 19 (2025): 7005–7016.

[136] A. Schizodimou and G. Kyriacou, “Acceleration of the Reduction of Carbon Dioxide in the Presence of Multivalent Cations,” Electrochimica Acta 78 (2012): 171–176.

[137] T. Pardal, S. Messias, M. Sousa, et al., “Syngas Production by Electrochemical CO₂ Reduction in an Ionic Liquid Based-Electrolyte,” Journal of CO2 Utilization 18 (2017): 62–72.

[138] B. A. Rosen, A. Salehi-Khojin, M. R. Thorson, et al., “Ionic Liquid–Mediated Selective Conversion of CO₂ to CO at Low Overpotentials,” Science 334, no. 6056 (2011): 643–644.

[139] X. Yang, X. Xiang, L. Zhou, et al., “Catalyst Design Strategies for Highly Efficient CO₂ Electroreduction,” Coordination Chemistry Reviews 536 (2025): 216650.

[140] S. Duan, H. Xu, J. Zhang, et al., “Benzimidazole-Linked Polymer Membranes for Efficient Syngas (H₂/CO/CO₂) Separation,” Journal of Membrane Science 717 (2025): 123595.

[141] S. Verma, S. Lu, and P. J. A. Kenis, “Co-Electrolysis of CO₂ and Glycerol as a Pathway to Carbon Chemicals With Improved Technoeconomics Due to Low Electricity Consumption,” Nature Energy 4, no. 6 (2019): 466–474.

[142] S. Wei, J. Zhu, X. Chen, et al., “Planar Chlorination Engineering Induced Symmetry-Broken Single-Atom Site Catalyst for Enhanced CO₂ Electroreduction,” Nature Communications 16, no. 1 (2025): 1652.

[143] H. Sun, L. Chen, Y. Lian, et al., “Topotactically Transformed Polygonal Mesopores on Ternary Layered Double Hydroxides Exposing Under-Coordinated Metal Centers for Accelerated Water Dissociation,” Advanced Materials 32, no. 20 (2020): 2006784.

[144] J. Leverett, R. Daiyan, L. Gong, et al., “Designing Undercoordinated Ni-N_x and Fe-N_x on Holey Graphene for Electrochemical CO₂ Conversion to Syngas,” ACS Nano 15, no. 7 (2021): 12006–12018.

[145] L. Peng, Y. Wang, I. Masood, et al., “Self-Growing Cu/Sn Bimetallic Electrocatalysts on Nitrogen-Doped Porous Carbon Cloth With 3D-Hierarchical Honeycomb Structure for Highly Active Carbon Dioxide Reduction,” Applied Catalysis, B: Environmental 264 (2020): 118447.

[146] F. Pan and Y. Yang, “Designing CO₂ Reduction Electrode Materials by Morphology and Interface Engineering,” Energy & Environmental Science 13, no. 8 (2020): 2275–2309.

[147] L. Luo, Z. Huang, and Q. Tang, “Computational Screening of a Promising Diatomic Catalyst for CO₂ Electroreduction to Syngas,” Journal of Materials Chemistry A 12, no. 9 (2024): 5145–5155.

[148] S. Jovanovic, P. Jakes, S. Merz, D. T. Daniel, R.-A. Eichel, and J. Granwehr, “In Operando NMR Investigations of the Aqueous Electrolyte Chemistry During Electrolytic CO₂ Reduction,” Communications Chemistry 6, no. 1 (2023): 268.

[149] W. Shan, R. Liu, H. Zhao, et al., “In Situ Surface-Enhanced Raman Spectroscopic Evidence on the Origin of Selectivity in CO₂ Electrocatalytic Reduction,” ACS Nano 14, no. 9 (2020): 11363–11372.

[150] D. Liu, S. Lai, X. Liao, S. Chen, T. Liu, and Y. Jiang, “Tandem Electrocatalytic Reduction With Syngas Fermentation for CO₂ Conversion to Multicarbon Products,” Journal of Environmental Chemical Engineering 13, no. 2 (2025): 115471.

[151] Y. Kim, E. W. Lees, C. Donde, et al., “Integrated CO₂ Capture and Conversion to Form Syngas,” Joule 8, no. 12 (2024): 3106–3125.

[152] M. A. Bajada, S. Roy, J. Warnan, et al., “A Precious-Metal-Free Hybrid Electrolyzer for Alcohol Oxidation Coupled to CO₂-to-Syngas Conversion,” Angewandte Chemie International Edition 59, no. 36 (2020): 15633–15641.

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