Stabilizing Cu⁰-Cu^δ+ sites via ohmic contact interface engineering for ampere-level nitrate electroreduction to ammonia

The synergistic Cu⁰-Cu^δ+ sites are found as the active sites for NH₃ synthesis through nitrate electroreduction reaction, but still face significant challenges in stabilizing the Cu^δ+ due to its self-reduction. Here we propose an Ohmic contact interface engineering strategy by loading copper nano-islands on indium hydroxide nanocubes. Attributed to the lower work function of Cu than that of In(OH)₃ with n-type semiconductor nature, the electrons in Cu can transfer unimpededly to In(OH)₃ at the interface of Ohmic junction, triggering and stabilizing polarized Cu⁰-Cu^δ+ active sites. Cu@In(OH)₃ sustains both high NH₃ yield rate (4.28 mmol h⁻¹ mg_cat.⁻¹) and Faradaic efficiency (97.35%) at −0.6 V vs. RHE, while maintaining stability for at least 120 h under an Ampere-level of 800 mA cm⁻². Such Ohmic contact interface engineering approach allows for simultaneously constructing and stabilizing the Cu⁰-Cu^δ+ for the electrosynthesis of ammonia, as well as other value-added chemicals relying on above active sites.