Anion‐Regulated Active Nickel Site for Nitrate Reduction in Efficient Ammonia Electrosynthesis and Zn‐Nitrate Battery

Abstract Electrocatalytic nitrate reduction (NO ₃ RR) to ammonia (NH ₃ ) has great potential to address the challenges caused by the Habor‐Bosch process. However, sluggish kinetic, complex mechanisms and competitive reactions seriously reduce the Faradaic efficiency (FE) and yield of NH ₃ . Transition metal‐based compounds are promising catalysts for electrocatalytic NO ₃ RR, where anions can tune the electronic structure of metal cation sites. In this work, oxygen (O) and phosphorus (P) anions are introduced to regulate the electronic structure of nickel (Ni) and reveal the mechanism of the anion regulation in electrocatalytic NO ₃ RR. The electrosynthesis performance of NH ₃ is ranked as follows: Ni ₂ P surpasses Ni, which in turn outperforms NiO. Notably, Ni ₂ P nanosheets exhibit a maximum FE of 97.4% for NH ₃ and a yield of 15.4 mg h ⁻ ¹ cm ⁻² . Characterization and theoretical calculation indicate that the introduction of the phosphorus anion moderately alters the electronic structure of Ni, resulting in reduced energy barriers for the rate‐limiting step of NO ₃ RR and improved H ₂ O decomposition to generate active hydrogen, which subsequently enhances NH ₃ production. This work highlights the critical role of anion regulation in electrocatalytic NO ₃ RR.