Triple Synergy Engineering via Metal‐Free Dual‐Atom Incorporation for Self‐Sustaining Acidic Ammonia Electrosynthesis

Abstract Electrochemical nitrate reduction reaction (NO 3 RR) for ammonia synthesis under acidic conditions offers significant advantages, like direct fertilizer production and prevention of ammonia volatilization. However, three critical challenges persist: instability of metal‐based catalysts, competition from the hydrogen evolution reaction (HER), and proton depletion leading to species imbalance. Here, we developed a novel metal‐free heteronuclear diatomic‐based catalyst that simultaneously addresses these challenges through atomic‐level triple synergy engineering. Silicon–iodine dual‐atoms are precisely anchored on nickel oxide ultrathin nanosheets supported on carbon cloth (Si/I‐NiO@CC) via a gradient‐heating co‐loading method. Si/I‐NiO@CC establishes a self‐sustaining catalytic system, achieving a remarkable Faradaic efficiency of 96.8% at −0.3 V versus RHE and record‐breaking operational stability of 420 h in acidic electrolyte, surpassing the performance of all reported acid NO 3 RR electrocatalysts to date. Advanced in situ spectroscopic characterization combined with electrochemical evaluation reveals the triple synergy mechanism: electron‐deficient Ni δ⁺ and oxygen vacancies generate abundant active sites while mitigating HER competition, iodine‐mediated proton reservoirs dynamically regulate H* coverage to maintain species balance, and covalent Si─O─Ni interfacial bonding inhibits metal leaching and stabilizes the catalytic system. This work establishes a constructive guideline for the rational engineering of high‐efficiency electrocatalysts for selective acidic NO 3 RR.