Dynamic Stabilization of Cuδ+ in Heterostructured Ag0-CuAgOx for High-Performing Nitrate Electroreduction

Abstract

Oxide-derived copper (OD-Cu) has exhibited significant promise in nitrate electroreduction reaction (NO₃RR) 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 NO₃RR, 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 Ag⁰-CuAgO_x. Operando X-ray absorption spectroscopy and diffuse reflection infrared Fourier transform spectroscopy reveal a strong correlation between NH₃ production and Cu^δ+ content in Ag⁰-CuAgO_x, with peak performance achieved when Cu⁺ is maximized. Ag⁰ acts as an electron acceptor, preventing the over-reduction of Cu^δ+ during NO₃RR. The stabilized Cu⁺ in Ag⁰-CuAgO_x helps achieve outstanding long-term stability of 400 h for NH₃ production, surpassing most of the state-of-the-art Cu-based electrocatalysts. Computational studies and ultraviolet photoelectron spectrometer confirm that Ag⁰ functions as the electronic buffer and enables electron transfer from Cu₂O to Ag to generate electron-deficient Cu sites, thus turning the Cu d-band center with favorable adsorption energies for key intermediates to facilitate NH₃ formation. The study paves the way to develop valence-stabilized catalysts for a range of electroreduction reactions.