▎ 摘　　要

In this study, we report sulfur-doped three-dimensional graphene (S-3DG) as a metal-free electrocatalyst for N-2 reduction reaction (NRR) under ambient conditions. Due to the high electron transport capacity and stable physicochemical properties of 3DG, it was utilized to improve the NRR catalytic performance dramatically. Hence, in 0.05 M H2SO4 the S-3DG achieved a remarkably large NH3 yield of 38.81 mu g(NH3) mg(cat)(-1) h(-1) and a high faradaic efficiency of 7.72% at -0.6 V versus a reversible hydrogen electrode (RHE), which is superior to most non-metal catalysts. Notably, it shows such outstanding selectivity that no hydrazine by-products were detected and the electrochemical stability passed a long-term durability test.