Potential-Induced Synthesis and Structural Identification of Oxide-Derived Cu Electrocatalysts for Selective Nitrate Reduction to Ammonia

Developing effective electrocatalysts for nitrate reductiontoammonia is paramount for ammonia synthesis while addressing the waterpollutant issue. Identifying the active structure and its correlationwith catalytic behavior during the reaction process is essential andchallenging for the rational design of advanced electrocatalysts.Herein, starting from Cu2O particles with controllablecrystal facets, the electrochemically reconstituted Cu/Cu2O was fabricated as a suitable catalytic system, and the relationshipbetween the chemical state of copper and product selectivity in thenitrate reduction reaction was studied. At -0.9 V versus reversiblehydrogen electrode, the oxide-derived Cu-0 (OD-Cu) cubeachieved a high ammonia Faradaic efficiency of 93.9% and productivityof up to 219.8 mu mol h(-1) cm(-2), surpassing those of most Cu-based catalysts. In situ Raman analysis,well-designed pulsed electrolysis experiments, and theoretical calculationsshowed that ammonia was preferentially produced on OD-Cu at high reductionpotentials and the presence of the Cu/Cu2O interface favorednitrite formation at low reduction potentials. The high ammonia selectivityof the OD-Cu cube originated from the enhanced adsorption of nitrateand lower reaction barrier of the potential-determining step (*NH3 -> NH3). This work presents an effectivestrategy to boost electrocatalysis and offers an insight into thereal active phase and corresponding catalytic behavior of Cu-basedelectrocatalysts.