Activity and Selectivity Control in CO₂ Electroreduction to Multicarbon Products over CuO_<i>x</i> Catalysts via Electrolyte Design

The CO2 electroreduction reaction (CO2RR) to chemicals and fuels is of both fundamental and practical significance, since it would lead to a more efficient storage of renewable energy while closing the carbon cycle. Here we report enhanced activity and selectivity for the CO2RR to multicarbon hydrocarbons and alcohols (∼69% Faradaic efficiency and −45.5 mA cm–2 partial current density for C2+ at −1.0 V vs RHE) over O2-plasma-activated Cu catalysts via electrolyte design. Increasing the size of the alkali-metal cations in the electrolyte, in combination with the presence of subsurface oxygen species which favor their adsorption, significantly improved C–C coupling on CuOx electrodes. The coexistence of Cs+ and I– induced drastic restructuring of the CuOx surface, the formation of shaped particles containing stable CuI species, and a more favorable stabilization of the reaction intermediates and concomitant high C2+ selectivity. This work, combining both experiment and density functional theory, provides insights into the active sites and reaction mechanism of oxide-derived Cu catalysts for the CO2RR