Facet engineering of polycrystalline copper catalytic electrode through additive-assisted electrodeposition for nitrate reduction to ammonium

The electrocatalytic reduction of nitrate to ammonia has become an upsurge in recent years. This approach uses nitrate from wastewater as the nitrogen source for ammonia production, providing a sustainable alternative to address the challenges associated with the traditional Haber-Bosch process. However, the scheme to synthesize a promising catalyst for electrochemically selective conversion of nitrate toward ammonia is not yet fully developed. Here we present a facile strategy to prepare a high-performance copper (Cu) electrode with well-controlled crystalline structures by modifying additive concentrations in the electrodeposition bath. At the applied potential of -0.9 V (vs. SCE), the designer Cu electrode exhibits an ammonium Faradaic efficiency of 44 % with a nitrate conversion of 96 % and ammonium selectivity of 66 %. Further analysis suggest that the enhanced reduction performance is attributed to the selective exposure of both Cu(111) and Cu(110) facets on the Cu electrode, which facilitate the critical nitrate to nitrite conversion and suppress the competing hydrogen evolution reaction.