Highly selective and efficient electrocatalytic removal of low-concentration nitrate ions using self-supported porous Ni0.8Cu0.2O@CuO heterostructure arrays

The electrocatalytic conversion of nitrate (NO 3 − ) to nitrogen (N 2 ) is a promising strategy for addressing the global issue of NO 3 − pollution in surface water and groundwater. However, the scarcity of efficient denitrification catalysts hinders the development of the aforementioned process, particularly at low NO 3 − concentrations. Herein, a self-supporting array of defect-rich heterostructured nanowires (Ni 0.8 Cu 0.2 O@CuO@NF) was synthesized for highly selective reduction of NO 3 − to N 2 . The introduction of Cu accelerated the rate-limiting step (NO 3 − to NO 2 − ), and the presence of defect-rich heterojunctions increased the catalytic active sites of the catalyst, thereby accelerating the reduction of NO 3 − and improving the selectivity towards N 2 . Ni 0.8 Cu 0.2 O@CuO@NF exhibited excellent denitrification capacity, with approximately 100% of NO 3 − degradation and 99.9% of N 2 selectivity under optimum parameter conditions, as well as ultra-high stability during the 8-cycle test. Significantly, NO 3 − conversion and N 2 selectivity for actual wastewater with complex ingredients were 70.7% and 99.1%, respectively. This study presents a novel concept for the development of cost-effective and highly effective catalysts for water and environmental restoration.