Locally Water‐Rich Interfacial Microenvironment Enables Self‐Powered High‐Current Ammonia Electrosynthesis

ABSTRACT Electrochemical nitrate‐to‐ammonia conversion holds great promise for sustainable nitrogen fixation, yet its industrial‑level current density operation is limited by cathodic active hydrogen (*H) supply shortage and high energy consumption caused by anodic oxygen evolution reaction (OER). Here, we develop a bifunctional CoP electrocatalyst with engineered phosphorus vacancies that generate atomic‐scale electric fields to enrich interfacial water molecules via enhanced hydrogen‐bonding interactions, alleviating local water scarcity caused by double‐layer compression under high nitrate concentrations and promoting *H generation for nitrate reduction reaction (NO 3 RR). Meanwhile, we replace OER with the thermodynamically favorable hydrazine oxidation reaction (HzOR), and the electrocatalyst promotes *OH adsorption to facilitate hydrazine dehydrogenation in HzOR. The resulting NO 3 RR||HzOR electrolyzer delivers an ammonia yield of 49.64 mg h −1 cm −2 at 500 mA cm −2 with a cell voltage of 0.962 V, and enables self‐powered ammonia production at 0.769 g L −1 h −1 without external energy input. This work reveals atomic‐scale electric field engineering as an effective strategy to modulate interfacial microenvironment for high‐performance, low‐energy ammonia electrosynthesis.