d‐Band center engineering of Cu active sites breaks activity–stability trade‐offs in nitrate‐to‐ammonia electroreduction

Abstract

Copper‐based catalysts dominate electrocatalytic nitrate reduction to ammonia (NO ₃ RR), yet suffer from an intrinsic activity‐stability trade‐off due to strong NH ₃ intermediates adsorption on Cu active sites, which accelerates catalyst deactivation at high activities. Herein, we regulate the d‐band center (εd) of Cu sites through Cu ⁺ /Cu ⁰ heterostructure engineering to facilitate NH ₃ desorption while preserving efficient nitrate conversion. Electrochemical kinetics and DFT calculations identify NH ₃ desorption as a critical kinetic limitation during NO ₃ RR and reveal that εd downshifting weakens NH ₃ binding and promotes its removal from the catalyst surface. This electronic modulation simultaneously suppresses Cu leaching (7.9‐fold reduction) and lowers the NH ₃ desorption barrier. The optimized catalyst achieves an NH ₃ yield rate of 6.6 mg h ⁻¹ mg _cat ⁻¹ with a Faradaic efficiency of 97.9% at −0.8 V in 500 ppm KNO ₃ , while retaining over 95% activity after 24 consecutive cycles. This work establishes electronic‐structure regulation as an effective strategy for durable, high‐performance NO ₃ RR catalysts.