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

The electrochemical carbon dioxide reduction reaction (eCO₂RR) involves numerous intermediates and simultaneous interactions between these intermediates and water (H₂O) molecules. Although extensive research has focused on stabilizing the carbon-related intermediates, limited attention has been paid to investigating the local regulations of H₂O molecules at molecular level. Considering the electrocatalytic interface, H₂O is critical during CO₂RR process, as H₂O molecules are directly involved in CO₂ 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 H₂O molecules on CO₂ electroreduction selectivity. We find, by enhancing the participation of isolated H₂O molecules, instead of asymmetric H-bonded H₂O or ice-like H₂O, in the local electrocatalytic microenvironment during CO₂ reduction process, that the cathodic products remarkably change from 95% C₁ FE to 70% C₂ FE. We unveil, via in situ ATR-SEIRAS measurement, that the H₂O microenvironment regulation can promote the formation of key intermediates, thus tuning the CO₂ reduction pathways.