Promoting Electrocatalytic CO₂ Reduction via Oxophilic Amorphous Metal Oxide-Mediated Interfacial Water Activation...

Interfacial water serves as the intrinsic proton source for CO₂ hydrogenation, yet synchronizing its activation with on-demand active hydrogen (^*H) supply without triggering the hydrogen evolution reaction (HER) remains challenging. Herein, we construct an oxophilic amorphous MnO_x overlayer on Ag to regulate the interfacial water network. In situ characterization and theoretical calculations demonstrate that under over 45% of interfacial water reorganizes into an ordered four-coordinate hydrogen-bonded (4-HB-H₂O) structure under operation, facilitating targeted proton transfer to CO₂ reduction intermediates. The distorted Mn-O polyhedra lower the water dissociation barrier by 0.54 eV while raising the HER barrier by 0.61 eV. It achieves a CO production rate of 12.8 mol h^-1 g^-1 and 68.6% Faraday efficiency (FE) at -1000 mA cm^-2 and maintains >95% FE_CO over 500 h at -200 mA cm^-2. It also enables efficient nitrate-to-ammonia conversion with the FE of 88.5 %, and the maximum NH₃ production rate is 831.4 mmol h^-1 g^-1, and a Zn-CO₂ rechargeable battery with FE_CO of 98.5% and power density of 2.1 mW cm^-2. This study underscores the amorphous metal oxide-mediated interfacial water activation as a versatile and scalable strategy for enhancing selectivity in water-involved electrocatalytic reactions.