Promoting Active Hydrogen Supply and Nitrate Adsorption by Disordering Tetrahedral‐Octahedral Structure of CuAl 2 O 4‐δ for Efficient Nitrate Reduction

Abstract Modulating the local coordination environment can optimize the electronic structure and reaction pathway of nitrate reduction to ammonia (NO 3 RR), beneficial to enhance the catalytic activity and selectivity. Herein, a disordered tetrahedral‐octahedral structure of CuAl 2 O 4‐δ (CAO) is proposed by Co doping as an efficient catalyst. Theoretical calculations reveal Co doping induces strong Co‐Al orbital interactions at octahedral sites, which lowers the energy barrier for water dissociation, and meanwhile, Oxygen vacancies (Vos) induced by Co doping not only enhance NO 3 − adsorption, but also serve as reservoir sites for transient * H storage, thereby promoting hydrogenation steps. The synergistic Cu‐Vo interaction facilitates the conversion of * NO 3 – to * NO 2 – and the interfacial electron transfer between Co and Cu suppresses the hydrogen evolution reaction (HER). The substitution of 30% Co in CAO (Co‐3) nanofibers creates the most Vos, resulting in a high Faradaic efficiency (FE) of 92.00% and a substantial NH 3 yield rate of 27.86 mg h −1 mg −1 cat. in neutral media. Additionally, it exhibits exceptional long‐term electrochemical durability and chemical stability. Thermodynamic analysis unveils the potential‐determining step of * NO 2 to * NO for Co‐3 possesses a low free energy of only 0.05 eV, highly superior to 0.29 eV for the pristine CAO.