The promotion of nitrate conversion into ammonia via the construction of tandem dual active sites of copper and cuprous oxide†

Abstract

Electrocatalytic nitrate reduction reaction (eNitRR) plays an essential role in maintaining the nitrogen cycle balance and the development of carbon-free energy sources. However, the complex reduction processes result in the preparation of ammonia with low Faraday efficiency and selectivity. Here, we constructed a tandem catalyst composed of dual active sites of copper and cuprous oxide by a facile electrodeposition technique, which effectively promotes the adsorption of nitrate and the conversion of nitrite, achieving a high Faraday efficiency of 95.8% and ammonia yield of 1.583 mmol h⁻¹ cm⁻². Density Functional Theory (DFT) calculations revealed that the Cu₂O surface could significantly reduce the energy barrier associated with NO₃⁻ adsorption, and the Cu component could capture the *NO₂ produced by the Cu₂O component in time for the subsequent reaction. Furthermore, when the catalyst was used as the cathode of the Zn–NO₃⁻ cell, the assembled cell achieved an open-circuit voltage of 1.37 V and a power density of as high as 3.78 mW cm⁻² in neutral electrolyte. This study provides new insights into the mechanism of electrocatalytic NH₃ production.