Molecular Scale Interfacial Water Management Switching Reaction Pathway of Carbon Dioxide Electroreduction

Abstract The electrochemical carbon dioxide reduction reaction (eCO 2 RR) involves numerous intermediates and simultaneous interactions between these intermediates and water (H 2 O) molecules. Although extensive research has focused on stabilizing the carbon‐related intermediates, limited attention has been paid to investigating the local regulations of H 2 O molecules at molecular level. Considering the electrocatalytic interface, H 2 O is critical during CO 2 RR process, as H 2 O molecules are directly involved in CO 2 reduction process or indirectly modify the solid–liquid interfacial structure, thereby impacting the reaction process. In this study, we use a model copper‐based catalyst containing palladium and indium dopants that have different hydrogen and oxygen adsorption capabilities to investigate the influence of H 2 O molecules on CO 2 electroreduction selectivity. We find, by enhancing the participation of isolated H 2 O molecules, instead of asymmetric H‐bonded H 2 O or ice‐like H 2 O, in the local electrocatalytic microenvironment during CO 2 reduction process, that the cathodic products remarkably change from 95% C 1 FE to 70% C 2 FE. We unveil, via in situ ATR‐SEIRAS measurement, that the H 2 O microenvironment regulation can promote the formation of key intermediates, thus tuning the CO 2 reduction pathways.