The Role of Interfacial Water in CO₂ Electrolysis over Ni‐N‐C Catalyst in a Membrane Electrode Assembly Electrolyzer

Abstract CO₂ electrolysis is a promising route for achieving net‐zero emission through decarbonization. To realize CO₂ 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 CO₂ 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 cm² 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 CO₂ electrolysis performance.