CuNi-modified nickel foam electrode for nitrate electrochemical reduction in water

Electrochemical reduction is an efficient method for treating high-concentration nitrate wastewater, providing benefits such as enhanced controllability and the elimination of secondary pollution. In this study, the CuNi/NF electrode was fabricated by direct current electrodeposition of copper and nickel onto nickel foam, which served as the cathode for the electrochemical reduction of nitrate. The electrode demonstrated superior nitrate removal performance, achieving an NO₃^--N removal rate of 83% after 5 h of reaction at an initial concentration of 500 mg/L, significantly outperforming the Cu/NF electrode (76%) and Ni/NF electrode (57%). The influence of key operating parameters on nitrate reduction was systematically investigated. The results indicated that the electrode prepared with a deposition time of 20 min exhibited the highest removal efficiency. Under optimal conditions (current density of 25 mA/cm², Cl^- concentration of 2 g/L, and initial pH of 7), the NO₃^--N removal rate reached 85%, with N₂ selectivity as high as 93.7%. The CuNi/NF electrode also exhibited good stability over five consecutive cycles. Finally, a plausible mechanism for nitrate reduction was proposed. This study provides fundamental data and theoretical support for the practical application of electrochemical methods in treating high-concentration nitrate wastewater.