Enhancement of Selective Electrocatalytic NO3 - Reduction to NH3 Over rGO-Coated Cu2O Nanoparticles

It is a green and feasible approach to realize artificial nitrogen cycling through the electrocatalytic reduction of nitrate (NO3-) into ammonia (NH3). Nevertheless, the electrochemical nitrate-to-ammonia reduction reaction (NO3-RR) has been greatly hindered by low Faradaic efficiency and high applied overpotential. Herein, a few-layer reduced graphene oxide (rGO)-coated Cu2O nanocrystal composite (denoted as Cu2O@rGO) is successfully constructed by the simple hydrothermal methodology to enhance the catalytic performance of NO3-RR to NH3. Benefiting from the synergistic effects of rapid electron migration, enriched oxygen vacancies, and intimate interface, the obtained Cu2O@rGO catalyst accelerates the adsorption of NO3- and some key intermediates and inhibits the hydrogen evolution reaction (HER) during the NO3-RR. Consequently, the optimized Cu2O@rGO catalyst exhibits NH3 Faradaic efficiency (FE) of 91.8% at -0.9 V, selectivity of up to 99%, and yield rate of 0.25 mmol<middle dot>h(-1)<middle dot>mg(cat)(-1), much outperforming the most reported Cu-based catalysts. Moreover, the in situ infrared spectroscopy (FT-IR) displays the formation pathway of key intermediates in the catalytic process and discloses the catalytic mechanism. This work presents a simple and effective methodology to improve the activity of Cu-based electrocatalysts for the NO3-RR to NH3 production.