Modulating Intermediate Adsorption and Interfacial Water Structure to Unlock the Potential of Nickel for Ammonia Electrosynthesis and Zn‐NO ₃ ⁻ Battery

Abstract

ABSTRACT Metallic Ni stands out to be a promising electrocatalyst for nitrate reduction reaction (NO 3 RR) to ammonia (NH 3 ), yet is bottlenecked by limited water dissociation kinetics for active hydrogen (*H) supply particularly at low potentials and insufficient adsorption/activation capability toward NO 3 − . We unveil for the first time that NO 3 RR performance of Ni can be activated by synergistic unconventional phase design and alloying engineering. Specifically, anomalous hcp Ni with Cu alloying (NiCu‐hcp) is readily engineered via a facile metal–organic frameworks mediated route. Impressively, the NiCu‐hcp can deliver prominent NO 3 RR performance with record NH 3 yield rate of 2.24 mmol h − 1 cm − 2 and Faradaic efficiency of 98.3% at −0.4 V versus RHE, favorably rivaling the state‐of‐the‐art ones. Moreover, integrating NiCu‐hcp into Zn‐NO 3 − battery delivers eminently high power density of 23.9 mW cm − 2 . From experimental and theoretical studies, unusual hcp phase together with Cu alloying engineering over Ni can regulate interfacial water structure for facilitated dissociation to generate *H, and meanwhile, manipulate electronic state, thereby promoting NO 3 − affinity/activation and lowering Gibbs free energy barrier of the rate‐determining step (*NO→*NOH). This contribution presents a new paradigm to unlock the potential of Ni for NO 3 RR via elegant unusual phase design synergistic with alloying engineering.