The Role of Interfacial Water in CO Electrolysis over Ni-N-C Catalyst in a Membrane Electrode Assembly Electrolyzer.

CO electrolysis is a promising route for achieving net-zero emission through decarbonization. To realize CO electrolysis toward practical application, beyond catalyst structures, it is also critical to rationally manipulate catalyst microenvironments such as the water at the electrode/electrolyte interface. Here, the role of interfacial water in CO electrolysis over Ni-N-C catalyst modified with different polymers is investigated. Benefiting from a hydrophilic electrode/electrolyte interface, the Ni-N-C catalyst modified with quaternary ammonia poly(N-methyl-piperidine-co-p-terphenyl) shows a Faradaic efficiency of 95% and a partial current density of 665 mA cm for CO production in an alkaline membrane electrode assembly electrolyzer. A scale-up demonstration using a 100 cm electrolyzer achieves a CO production rate of 514 mL min at a current of 80 A. In-situ microscopy and spectroscopy measurements indicate that the hydrophilic interface significantly promotes the formation of the *COOH intermediate, rationalizing the high CO electrolysis performance.