Electrochemical Reconstruction of Copper Oxide into Metallic Copper Nanostructures for Enhanced Electrochemical Nitrate Reduction to Ammonia

Ammonia plays an important role in the global economy. Currently, its production is almost entirely dependent on the Haber–Bosch process, a highly energy-consuming method with significant CO 2 emissions. Developing alternative ammonia synthesis methods is essential to achieve a sustainable and carbon-neutral future. The electrocatalytic nitrate reduction reaction (ENO 3 RR) offers a promising pathway for NH 3 synthesis due to its operational simplicity, high energy efficiency, and minimal environmental impact. In this work, we present the reconstruction of N-doped carbon (CN x ) supported CuO into under-coordinated metallic Copper/CN x and utilize it for the electrochemical reduction of nitrates to ammonia. The catalyst achieves an NH 3 production rate of 0.8 mmolh –1 cm –2 and FE of approximately 86% at a potential of −0.5 V (RHE). The enhanced ENO 3 RR performance of the composite results from the under-coordinated active sites of copper, high ECSA, its porous structure, etc. In situ Raman spectroscopy confirms that metallic copper is formed during ENO 3 RR. The DFT study indicates that the high catalytic activity for nitrate-to-ammonia conversion is more favorable on the Cu(111) surface than on the CuO(111) surface. The transition from *NO to *NOH on the Cu(111) surface has an energy barrier of 0.35 eV, with a more spontaneous *NO to *N step than CuO(111). This strategy opens new possibilities for designing high-efficiency electrocatalysts through electrochemical surface modification, facilitating the selective nitrate reduction to ammonia.