Dynamic Stabilization of Cu^δ+ in Heterostructured Ag⁰‐CuAgO_x for High‐Performing Nitrate Electroreduction

Abstract Oxide‐derived copper (OD‐Cu) has exhibited significant promise in nitrate electroreduction reaction (NO 3 RR) due to their hybrid Cu oxide states (Cu δ+ ) for stabilizing key reaction intermediates. However, owing to the intrinsic vulnerability of Cu δ+ reduction during NO 3 RR, it is still challenging to develop highly active and durable OD‐Cu catalysts. Herein, a unique strategy is reported to stabilize the Cu + state by dynamically introducing metallic Ag clusters in the oxidized CuAgO x nanosheets to form heterostructure Ag 0 ‐CuAgO x . Operando X‐ray absorption spectroscopy and diffuse reflection infrared Fourier transform spectroscopy reveal a strong correlation between NH 3 production and Cu δ+ content in Ag 0 ‐CuAgO x , with peak performance achieved when Cu + is maximized. Ag 0 acts as an electron acceptor, preventing the over‐reduction of Cu δ+ during NO 3 RR. The stabilized Cu + in Ag 0 ‐CuAgO x helps achieve outstanding long‐term stability of 400 h for NH 3 production, surpassing most of the state‐of‐the‐art Cu‐based electrocatalysts. Computational studies and ultraviolet photoelectron spectrometer confirm that Ag 0 functions as the electronic buffer and enables electron transfer from Cu 2 O to Ag to generate electron‐deficient Cu sites, thus turning the Cu d‐band center with favorable adsorption energies for key intermediates to facilitate NH 3 formation. The study paves the way to develop valence‐stabilized catalysts for a range of electroreduction reactions.