Single‐Site Polyoxometalate Complexes with Engineered Electron Channels for Efficient Electrocatalytic Ammonia Synthesis from Nitrate

Abstract Electrochemical nitrate reduction to ammonia (ENRA) is a sustainable approach for the electrosynthesis of ammonia (NH 3 ) and the purification of wastewater. Herein, three polyoxometalate‐based (POM‐based) mononuclear complexes, namely [M(HNCP) 2 (H 2 O)][PW 12 O 40 ]·H 2 O (HNCP = 4‐(1H‐imidazo[4,5‐f][1,10]phenanthrolin‐2‐yl)benzoic acid; M = Ni, Co, Zn, referred to as M‐PW 12 ), that feature atomically dispersed metal sites are prepared. Among them, Ni‐PW 12 exhibits outstanding ENRA performance, with a Faradaic efficiency (FE) of 90.3% and an NH 3 yield rate of 11.2 mg h −1 mg cat. −1 at −1.3 V versus reversible hydrogen electrode (RHE). An in‐depth computational study reveals that directional electron transfer from the POM cluster to the metal center diminishes the energy barrier associated with the rate‐determining step ( * N → * NH) and improves protonation energetics along the NO 3 − to NH 3 pathway. This study demonstrates that electron‐transfer engineering via POM–metal‐hybrid systems delivers a 24.1–39.3% enhancement in NH 3 FE compared to a POM‐only catalyst. The core mechanism lies in the electron transfer effect between POM and metal components: this effect optimizes the electronic structure of reaction active sites, suppresses the competitive hydrogen evolution reaction, and thus improves the selectivity of NH 3 generation. This work provides a concrete strategy for high‐performance POM‐based electrocatalysts and advancessustainable ammonia production.