The Role of Interfacial Water in CO 2 Electrolysis over Ni-N-C Catalyst in a Membrane Electrode Assembly Electrolyzer.

CO 2 electrolysis is a promising route for achieving net-zero emission through decarbonization. To realize CO 2 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 2 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 -2 for CO production in an alkaline membrane electrode assembly electrolyzer. A scale-up demonstration using a 100 cm 2 electrolyzer achieves a CO production rate of 514 mL min -1 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 2 electrolysis performance.