Advances in Cu-based catalysts for electroreduction of CO₂ to C₂H₄ in flow cells

Global investment in ethylene (C₂H₄) production via nonpetroleum pathways is rising, highlighting its growing importance in the energy and environmental sectors. The electroreduction of carbon dioxide (CO₂) to C₂H₄ in flow cells is emerging as a promising technology with broad practical applications. Direct delivery of gaseous CO₂ to the cathode catalyst layer overcomes mass transfer limitations, enhancing reaction rates and enabling high current density. This review summarizes recent research progress in the electrocatalytic CO₂ reduction reaction (eCO₂RR) for selective C₂H₄ production in flow cells. It outlines the principles of eCO₂RR to C₂H₄ and discusses the influence of copper-based catalyst morphology, crystal facet, oxidation state, surface modification strategy, and synergistic effects on catalytic performance. In addition, it highlights the compositional structure of the flow cell, and the selection and optimization of operating conditions, including gas diffusion electrodes, electrolytes, ion exchange membranes, and alternative anode reaction types beyond the oxygen evolution reaction. Finally, advances in machine learning are presented for accelerating catalyst screening and predicting dynamic changes in catalysts during reduction. This comprehensive review serves as a valuable reference for the development of efficient catalysts and the construction of electrolytic devices for the electrocatalytic reduction of CO₂ to C₂H₄.