▎ 摘　　要

Catalysts play a key role in hydrogen production as green energy carriers. We show herein for the first time that manganese impurities in graphene can improve the catalytic activity of synthesized N-doped graphene (NG) for the hydrogen evolution reaction in acid media by influencing the ratio of different N-functionalities. A 122 mV improvement in the overpotential was found following the Mn impregnation of graphene. Transmission electron microscopy images confirmed the formation of manganese oxide nanoparticles on the NG sheets. X-ray photoelectron spectroscopy revealed structural alteration in favor of higher quantities of quaternary and pyrrolic nitrogen functionalities, from approximately 37% in NG to 84% in the Mn-inserted-doped graphene catalyst. This enhanced catalytic performance, based on density functional theory calculations in the literature, was attributed to an increase in the number of active sites with higher activity.