Cu/Cu₂O/CuO Hierarchical Nanosheets for Electrocatalytic Conversion of Nitrate to Ammonia

Considering energy preservation and ecological conservation, the electrocatalytic reduction of nitrate wastewater to valuable ammonia (NO3RR) has broad application prospects. Nonetheless, multiple electron transfers and hydrogen evolution competition severely hinder the reaction kinetics and selectivity. Herein, Cu/Cu2O/CuO hierarchical nanosheets with a multiphase interface was designed by in situ electrochemical reconstruction. The 1D structure composed of vertically expanded nanosheets can reveal numerous active sites and facilitate the transfer of protons. Additionally, the electronic interaction and interface effect among Cu/Cu2O/CuO make it possible to regulate the Cu d band center and control the adsorption energies of the intermediates. Considering these benefits, Cu/Cu2O/CuO hierarchical nanosheets demonstrated superior Faraday efficiency (90.52%), remarkable ammonia selectivity (91.21%), and outstanding nitrate conversion (89.31%) for NO3RR at a low overpotential of −0.23 V vs RHE.