Roles of copper(I) in water-promoted CO2 electrolysis to multi-carbon compounds

The membrane electrode assembly (MEA) is promising for practical applications of the electrocatalytic CO2 reduction reaction (CO2RR) to multi-carbon (C2+) compounds. Water management is crucial in the MEA electrolyser without catholyte, but few studies have clarified whether the co-feeding water in cathode can enhance C2+ formation. Here, we report our discovery of pivotal roles of a suitable nanocomposite electrocatalyst with abundant Cu2O−Cu0 interfaces in accomplishing water-promoting effect on C2+ formation, achieving a current density of 1.0 A cm−2 and a 19% single-pass C2+ yield at 80% C2+ Faradaic efficiency in MEA. The operando characterizations confirm the co-existence of Cu+ with Cu0 during CO2RR at ampere-level current densities. Our studies reveal that Cu+ works for water activation and aids C‒C coupling by enhancing formations of adsorbed CO and CHO species. This work offers a strategy to boost CO2RR to C2+ compounds in industrial-relevant MEA by combining water management and electrocatalyst design. Water plays a key role in electrocatalytic CO2 reduction, but the role of catalyst in water management is unknown. Here, the authors report the importance of catalyst in determining the function of water and demonstrate that the catalyst containing Cu+ promotes water activation and C2+ formation.