Decoding the Role of e_g Orbital Occupancy in Co Sites: Mechanistic Insights into Enhanced N₂ Activation for Electrocatalytic Nitrate Synthesis

The electrochemical synthesis of nitrates through nitrogen oxidation reactions (NOR) faces challenges due to the chemical stability of N 2 and the complexity of its electron transfer mechanisms. Here, we report the enhancement of the NOR via Al doping into Co 3 O 4 . This doping modifies the electronic structure of Co 3 O 4, particularly by increasing the e g orbital occupation, which effectively activates N 2 . Our experimental results, corroborated by density functional theory (DFT) calculations, reveal that Al doping shortens Co–N bond lengths and elongates the N≡N bond, thereby enhancing N 2 polarization. The altered material, Al–Co 3 O 4, delivers a nitrate yield of 78.45 μg·h –1 ·mg cat –1 with a Faradaic efficiency of 11.91%. These improvements are attributed to an optimized electron configuration and enhanced adsorption characteristics due to the modified orbital occupancy. Our study highlights the crucial role of orbital engineering in enhancing electrocatalyst efficiency for nitrogen activation, offering a promising route for the advancement of NOR technology.