Electronic Confinement Induced Single Atom Functionality in Hydroxylamine Synthesis Unveiled by Constant Potential Simulation
Changgeng Wei, Huan Li, Qianxiao Wang, Chenyu Yang, Thomas Frauenheim, Jianping XiaoABSTRACT
Electrochemical nitric oxide (NO) reduction offers a sustainable route for hydroxylamine (NH 2 OH) synthesis. Single‐atom catalysts (SACs), featuring isolated metal centers and weaker adsorbate binding than extended metals, are widely regarded as ideal NH 2 OH‐selective catalysts. However, the recent observation of NH 2 OH production on highly reactive metals challenges this conventional viewpoint and indicates that SACs are not indispensable in hydroxylamine electrosynthesis. Here, we establish a unified picture in which electronic confinement induces single‐atom functionality that underlies NH 2 OH selectivity. Specifically, our constant‐potential simulations identify the competition between *HNO and *NOH formation as a key determinant of NH 2 OH versus NH 3 selectivity, with preferential *HNO formation directing the reaction toward NH 2 OH production. Grand canonical Monte Carlo simulations further reveal that highly reactive metals undergo operando surface restructuring, generating isolated metal centers that acquire single‐atom functionality and preferentially stabilize *HNO. Electronic structure analysis uncovers a unified origin of *HNO preference: heteroatom coordination induces strong orbital hybridization, narrowing the metal d‐band and localizing the electronic states of the isolated metal centers. This electronic confinement enables balanced *HNO‐metal interactions while preserving the intramolecular N─O bond, thereby stabilizing *HNO and promoting NH 2 OH selectivity. These findings establish electronic confinement as a promising and general design principle for developing NH 2 OH‐selective electrocatalysts beyond predefined SACs.