Unveiling the Corner-Sharing [Mn3+]- VO-[Mn3+] Active Sites in Manganese Oxides: How Structure-Defined Oxygen Vacancies Redirect the Nitrate Reduction Pathway Toward High-Rate Ammonia Synthesis

The nitrate reduction reaction (NO3- RR) offers an eco-friendly pathway for sustainable ammonia production, this research presents a novel NO3 -to NH3 conversion mechanisms by elucidating the structure-activity relationship between different [MnO6] octahedral connection modes and catalytic performance. The alpha-MnO2-160 catalyst rich in corner-positioned oxygen vacancies ([Mn3+] - VO- [Mn3+]) demonstrated the best performance, achieving a Faraday efficiency (FE) of 91.48% at -1.0 V vs. RHE and an NH3 production rate of 1540.9 mu mol h- 1 cm- 2 at -1.2 V vs. RHE, while maintaining stability during 15 h of continuous operation. The [Mn3+] - VO[Mn3+] structure, serving as a bimetallic active center, significantly enhances the NO3 -adsorption energy (-2.39 eV) and promotes N - O bond dissociation, while effectively reducing the energy barriers (-3.30 eV, -1.84 eV) of the *NOH -> *N -> *NH pathway and suppressing the conventional *NOH -> *NHOH pathway (-1.25 eV). This corner oxygen vacancy-induced electron rearrangement mechanism achieves precise regulation of the adsorption strength of reaction intermediates, providing a theoretical basis for designing high-performance Mnbased NO3- RR catalysts and demonstrating its potential in efficient catalysis as well as the development of energy and chemical industries.