Self-supported copper/copper oxide microspheres for efficient electrocatalytic removal of low-concentration nitrate from aqueous solutions

The electrochemical removal of nitrate (NO 3 − ) from aqueous solutions is a promising strategy for wastewater treatment; however, highly active catalysts are required. In this study, self-supported Cu/copper oxide (CuO) microspheres (ms) on Ni foam (NF) (Cu/CuOms/NF) were fabricated for NO 3 − removal from water using an electrochemical method, achieving a transformation efficiency of up to 99.72 % and N 2 selectivity of 97.97 %. Cu/CuOms/NF also exhibited excellent NO 3 − removal performance over a wide pH range, while maintaining extremely low levels of toxic ammonia residues. The Cu/CuOms/NF-driven NO 3 − removal rate remains as high as 95.45 % even after recycling for five times, demonstrating the remarkable electrochemical stability of the catalyst. The Cu/CuOms supported on NF provided active sites and accelerated the oxidation cycle involving Cl − , leading to the complete transformation of NO 3 − into harmless N 2 gas. Therefore, this study not only achieved the environmentally friendly treatment of NO 3 − pollutants in wastewater but also provided a promising strategy for developing catalysts for electrochemical NO 3 − removal.