A Cu0.76Co2.24O4/γ-Cu2(OH)3Cl composite catalyst for efficient neutral nitrate reduction

Abstract

The electrocatalytic nitrate reduction reaction (eNO₃⁻RR) is an environmentally friendly process that converts nitrate wastewater into high-value ammonia (NH₃). However, the multi-step electron and proton transfer in this reaction leads to slow kinetics and competitive reactions, making it challenging to achieve energy-efficient performance. Herein, a Cu_0.76Co_2.24O₄/γ-Cu₂(OH)₃Cl (CCOC) composite has been prepared as an electrocatalyst for the eNO₃⁻RR. The CCOC catalyst demonstrated an outstanding NH₃ yield rate of 10.71 mg h⁻¹ cm⁻² and a remarkable faradaic efficiency (FE) of 95.9% in a 0.5 M Na₂SO₄ neutral solution containing 0.1 M NO₃⁻, surpassing most reported catalysts under neutral conditions. In situ investigations demonstrated that Cu_0.76Co_2.24O₄ with high-valent Cu^δ+ and Co^δ+ significantly enhances H₂O dissociation and proton production while also promoting the adsorption of NO₃⁻ and *NH intermediates. These properties contribute to the high NH₃ selectivity and activity observed under neutral conditions. This work demonstrates Cu_0.76Co_2.24O₄/γ-Cu₂(OH)₃Cl as a promising candidate for the sustainable and efficient production of NH₃ through the eNO₃⁻RR, offering new insights into efficient nitrate reduction in neutral environments.