Physical and electronic structure optimization of multivalent multi-dimensional Cu-based electrodes for efficient electrocatalytic nitrate reduction to ammonia

Abstract

The electrochemical reduction of nitrate for ammonia synthesis has attracted considerable attention due to its low energy consumption and environmental compatibility. To facilitate the industrial-scale implementation of catalysts for electrochemical ammonia production, it is crucial to consider not only the catalysts’ high catalytic activity and selectivity but also their scalable fabrication process and facile preparation methodology. This study presented a multi-dimensional composite electrode with multivalent Cu-based oxides designed using a simple immersion reduction method. Cu(OH)₂ nanowires and Cu₂O nanoparticles were in-situ grown on Cu foam, creating a multidimensional composite structure. Subsequently, the electrode is transformed into Cu⁺/Cu⁰ through electrochemical in-situ reduction, while the microstructure and morphology do not undergo significant changes. The electronic interactions between multivalent Cu-based oxides promoted physicochemical adsorption of NO₃^– molecules and optimize electron and proton transfer pathways. At a potential of −0.8 V (vs. RHE) in neutral electrolyte, the multivalent Cu-based electrode achieved the nitrate conversion of 99.99 %, NH₃ yield rate of 1040.82 µg h⁻¹ cm⁻² and NH₃ Selectivity of 99.5 %. Furthermore, the electrodes demonstrated high nitrate conversion and good NH₃ yield when powered by a small solar photovoltaic panel, suggesting potential for industrial-scale production using renewable energy sources.