Co-Doped CuO Nanoarrays for Enhanced Electrocatalytic Nitrate Reduction to Ammonia via Active Hydrogen Regulation
Zhexuan Li, Yaxuan Li, Song Cheng, Ling Fang, Fengjun Yin
Abstract
Electrocatalytic reduction of nitrate (NO 3 – RR) has emerged as a promising technique for nitrate pollutant treatment, providing a viable pathway for nitrate removal and ammonia production. Copper oxide (CuO) electrocatalysts are particularly advantageous due to their low cost and favorable d-orbital energy alignment with the π-orbitals of nitrate molecules, which facilitates nitrate adsorption on the CuO surface and promotes the NO 3 – RR. However, CuO exhibits low selectivity for NH 3 and is constrained by its low reduction rate at high potentials and competition with hydrogen evolution reactions at lower potentials, which hinders its practical application. To this end, cobalt-doped copper oxide nanoarrays (Co-doped CuO NAs) were hereby developed using a simple sequence of oxidation and hydrothermal methods. This nanostructure enhances the NO 3 – RR rate by providing additional active sites, thereby accelerating the reaction rate. Co doping effectively regulates the active hydrogen (H*) from water splitting, further enhancing the interaction with nitrate on the electrocatalyst surface and improving the NH 3 yield. Specifically, in this work, Co-doped CuO NAs achieved a Faradaic efficiency of 95.99 ± 2.63% for ammonia production at −0.63 V vs RHE, with a rate of 8.41 ± 0.14 mg h –1 cm –2 and an ammonia selectivity of 98.30 ± 1.44%.