Understanding\nthe Activity Trends in Electrocatalytic\nNitrate Reduction to Ammonia on Cu Catalysts

Abstract

Cu-based catalysts possess great potential in the electrocatalytic\nnitrate (NO₃^–) reduction reaction for\nammonia (NH₃) synthesis. However, the low atomic economy\nlimits their further application. Here we report a Cu single-atom\n(SA) incorporated in nitrogen-doped carbon (Cu SA/NC) with high atomic\neconomy, which exhibits superior NH₃ Faradaic efficiency\n(FE) of 100% along with an impressive NH₃ yield rate of\n7480 μg h^–1 mg_cat.^–1. As counterparts, Cu_s+n/NC, with mixed SA and nanoparticles\n(NPs), shows decreasing NH₃ FE with decreasing SA content,\nbut the production of N₂ and N₂O increases gradually,\nwhich reaches the maximum on pure Cu NPs. In situ characterizations\nand theoretical calculations reveal that a higher NH₃ FE\nof Cu SA/NC is ascribed to a lower free energy of the rate-limiting\nstep (HNO* → N*) and effective inhibition for the N-N coupled\nprocess. This work provides the intuitive activity trends of Cu-based\ncatalysts, opening an avenue for subsequent catalysts design.