▎ 摘　　要

Electrochemical N-2 fixation using renewable electricity in water provides a renewable route for artificial NH3 synthesis, whereas developing active and selective catalysts is highly necessary for an efficient N-2 reduction reaction (NRR) process. In this work, we report ultrasmall iridium nanoparticles on reduced graphene oxide (Ir/RGO) as an effective NRR electrocatalyst, achieving an NH3 yield of 55.6 mu g h(-1) mg(-1) with a faradaic efficiency of 15.3% at -0.3 V (RHE), outperforming most previously reported catalysts. Density functional theory calculations reveal that Ir is active for the NRR, while the RGO can further boost the NRR activity of supported Ir by imparting the enriched electrons on Ir that induce the upshift of the d-band center, resulting in enhanced N-2 adsorption and a decreased energy barrier for the potential-determining step.