Triple Synergy Engineering via Metal‐free Dual‐Atom Incorporation for Self‐sustaining Acidic Ammonia Electrosynthesis

Electrochemical nitrate reduction reaction (NO3RR) 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‐atom 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 vs. RHE and record‐breaking operational stability of 420‐h in acidic electrolyte, surpassing the performance of all reported acid NO3RR electrocatalysts to date. Advanced in situ spectroscopic characterization combined with electrochemical evaluation reveals the triple synergy mechanism: electron‐deficient Niδ+ and oxygen vacancies generate abundant active sites while mitigating HER competition, iodine‐mediated proton reservoir dynamically regulate H* coverage to maintain species balance, and covalent Si–O–Ni interfacial bonding inhibits metal leaching and stabilize the catalytic system. This work establishes a constructive guideline for the rational engineering of high‐efficiency electrocatalysts for selective acidic NO3RR.