Facile Tailoring of the Electronic Structure and the d-Band Center of Copper-Doped Cobaltate for Efficient Nitrate Electrochemical Hydrogenation

Electrocatalytic nitrate reduction is an effective strategy to eliminate nitrate’s environmental impact and produce high-value-added ammonia products. However, most of the current reports focus on preparation strategies of catalysts, with poor exploration of the mechanism. In this work, we fabricated a binding-free Cu-doped Co3O4 electrode (Cu–Co3O4) to reveal the structure–activity relationship. Cu–Co3O4 exhibited a maximum Faradaic efficiency of ammonia of up to 86.5% at −0.6 V vs reversible hydrogen electrode in a neutral electrolyte, with the corresponding yield rate of 36.71 mmol h–1 g–1. In situ electrochemical Raman spectroscopy confirmed that the structure of Cu–Co3O4 exhibits excellent stability and durability. Theoretical analysis revealed that the interaction between Cu and Co induces the d-band center position of the mono-metal oxide to shift toward the center to optimize the nitrate reduction intermediate hydrodeoxygenation free-energy change, especially of *NOx (x = 1, 2, and 3). These results offer guidelines for the electrochemical reduction of nitrate with transition metal oxide electrocatalysts.