Proton-Transfer Dynamics Regulates CO2 Electroreduction Products via Hydrogen Coverage.

Electrochemical conversion of CO2 to hydrocarbons is a promising approach to carbon neutrality and energy storage. The formation of reaction intermediates involves crucial steps of proton transfer, making it essential to understand the role of protons in the electrochemical process to control the product selectivity and elucidate the underlying catalytic reaction mechanism of the CO2 electrochemical reduction (CO2RR). In this work, we proposed a strategy to regulate product selectivities by tuning local proton transport rates through a surface resin layer over cuprous oxides. We systematically studied the influence of proton transfer rates on product selectivities by regulating the polymerization degree of resorcinol-formaldehyde resin (RF). The production of C2 compounds and CH4 could be switched through an RF coating with the maximum CH4 Faradaic efficiency of 51% achieved at current densities close to the amperage level. Both experimental and theoretical calculation results suggest that the resin layer can subtly alter proton transfer rates during the electrochemical process, thereby influencing the hydrogen coverage on catalytic sites and ultimately guiding the overall electrochemical performance toward product selectivity.