Pre-introduced alkali-metal cations enhance C ₂₊ faradaic efficiency in CO ₂ reduction

Abstract Alkali-metal cations enhance catalytic activity in CO 2 reduction reactions (CO 2 RRs) by providing an interface electric field enhancement effect and stabilizing CO 2 and CO 2 RR intermediates. Membrane electrode assemblies (MEAs) with zero-gap electrolyzers are expected to substantially improve selectivity and reaction rates by directly supplying CO 2 to the cathode and dramatically reducing resistance within the reactor. However, compared with the understanding of cation effects in conventional H-type reaction reactors, in which the cathode electrode is in contact with the electrolyte solution, the understanding of cation effects in MEA reactors is insufficient. In this study, we report that the C 2+ product selectivity of Cu-based catalysts is enhanced by pre-loading alkali-metal salts bearing hydrophobic counter-anions onto the cathode. Operando spectroscopic analysis suggests that alkali-metal cations increase the CO concentration on the catalyst surface and promote the formation of C–C coupling intermediate species. This method, which can enhance catalyst activity using a simple technique, is expected to significantly contribute to future catalyst and device development.