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

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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.

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