Nitrogen and Fluorine Dual-Doped Porous Graphene-Nanosheets as Efficient Metal-Free Electrocatalysts for Hydrogen-Evolution in Acidic Media
Nitrogen and fluorine dual-doped porous graphene-nanosheets (NFPGNS) with pyridinic N doping rich configurations have been synthesized by a simple ion adsorbed and chemical-etching method. Higher crystalline degree of graphitization of NFPGNS is better for charge transportation on surfaces of electrocatalysts. At the same time, higher surface areas and various pore structures of NFPGNS are beneficial for exposing more active sites accessible for electrolyte. Therefore, efficient catalytic activity towards hydrogen evolution reaction (HER) with the onset overpotential of only ~ 150 mV and superior stability have been performed on NFPGNS electrocatalysts. Doping of F obviously promotes the catalytic activity of N containing carbon materials for HER. Further density functional theory (DFT) calculations reveal the heteroatoms multi-doping effect on NFPGNS leading to a lowest Gibbs free energy and stronger strength of H adsorption, in favor of promoting HER catalytic activity.