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

Electrochemical nitrate reduction reaction (NORR) 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 NORR electrocatalysts to date. Advanced in situ spectroscopic characterization combined with electrochemical evaluation reveals the triple synergy mechanism: electron-deficient Ni 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 NORR.