Hollow Square Ni-Doped Copper Oxide Catalyst Boosting Electrocatalytic Nitrate Reduction

Abstract

The electrochemical nitrate reduction reaction to ammonia (NRA) is gaining increasing attention as an eco-friendly approach to convert harmful nitrate pollutants into high-value product ammonia. NRA involves two critical rate-determining steps: hydrogenation of the *NO and *NOH intermediates. The composite of Ni and Cu has been demonstrated to exhibit synergistic catalytic effects; however, research on the combination of Ni and CuO remains limited. Herein, an advanced Ni-doped copper oxide catalyst with a hollow square morphology (Ni–CuO) is reported with a Faradaic efficiency of 95.26% at −0.8 V vs RHE and a high yield rate of 0.94 mmol h^–1 cm^–2, demonstrating high selectivity and stability. Complementary analyses demonstrated that the active hydrogen generated at the Ni sites facilitates the hydrogenation of *NO_x adsorbed on Cu sites. Theoretical computations further confirm the thermodynamic viability of this bimetallic catalytic mechanism. Furthermore, an Al–NO₃^– battery with a high open-circuit voltage was constructed by using Ni–CuO as the cathode. This work presents a synergistically modulated catalyst for complex catalytic processes and introduces a highly efficient Al–NO₃^– battery capable of simultaneous NH₃ synthesis and electrical energy conversion, underscoring its potential in efficient catalysis and the development of the energy and chemical industries.