Deep self-reconstruction of CoF2 to hierarchically defective Co(OH)2 nanosheets for electrocatalytic reduction of nitrate to ammonia

Abstract

The electroreduction of nitrate to ammonia is a complicated reaction involving an eight-electron transfer process. Active and selective catalysts are necessary to achieve satisfactory conversion efficiency in this reaction. Due to their unique chemical properties, transition metal fluorides tend to form highly active hydroxides via electrochemical reconstruction. In this work, hierarchical Co(OH)₂ nanosheets with abundant defects were reconstructed in situ from CoF₂ nanosheets and used as efficient electrocatalysts for reducing nitrate to ammonia. In an alkaline solution containing 0.1 M NO₃⁻, the defect-rich Co(OH)₂ nanosheets exhibit a high ammonia production rate of 0.62 mmol h⁻¹ cm⁻², a faradaic efficiency of up to 94.3%, and outstanding stability. In situ characterization and theoretical calculations were employed to reveal the catalytic mechanism.