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

Abstract

The electrocatalytic conversion of nitrate (NO3−) to nitrogen (N2) is a promising strategy for addressing the global issue of NO3− pollution in surface water and groundwater. However, the scarcity of efficient denitrification catalysts hinders the development of the aforementioned process, particularly at low NO3− concentrations. Herein, a self-supporting array of defect-rich heterostructured nanowires (Ni0.8Cu0.2O@CuO@NF) was synthesized for highly selective reduction of NO3− to N2. The introduction of Cu accelerated the rate-limiting step (NO3− to NO2−), and the presence of defect-rich heterojunctions increased the catalytic active sites of the catalyst, thereby accelerating the reduction of NO3− and improving the selectivity towards N2. Ni0.8Cu0.2O@CuO@NF exhibited excellent denitrification capacity, with approximately 100% of NO3− degradation and 99.9% of N2 selectivity under optimum parameter conditions, as well as ultra-high stability during the 8-cycle test. Significantly, NO3− conversion and N2 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.