▎ 摘　　要

As a kind of clean and high efficient energy conversion devices, the proton exchange membrane fuel cell (PEMFC) is a promising technology for clean and sustainable power generation. Metal-coordinated nitrogen-doped graphene is attractive since its use as a cathode material for the PEMFC. The mechanism of O-2 activation and hydrogenation on TiN4 embedded graphene has been investigated in terms of the dispersion-corrected density functional theory (DFT-D) method. It is found that: 1) O-2 prefers to stay on top of the Ti atom with the side-on configuration, forming the O-Ti-O three-member ring with an adsorption energy of 4.96 eV. 2) According to the Mulliken atomic charges analysis, the absorbed O-2 molecule are negatively charged by 0.60 e in the side-on configuration. 3) Upon the chemisorption of the O-2 on TiN4-graphene, there are two possible pathways during the activation of the O-2 molecule: dissociation and hydrogenation. In the dissociation pathway, the adsorbed O-2 molecule is first dissociated into two O atoms, with a fairly big reaction barrier of 0.95 eV and an endothermic reaction energy of 0.20 eV. Subsequently, the two O atoms are hydrogenated into O+ OH with a reaction barrier of 0.40 eV and an exothermic reaction energy of 2.46 eV. In the hydrogenation pathway, the reaction barrier of the hydrogenation of the adsorbed O-2 is 0.52 eV. The OOH formed subsequently is dissociated into O+ OH with a small reaction barrier of 0.04 eV and an exothermic reaction of 2.14 eV. The hydrogenation pathways of the adsorbed O-2 is more preferable, and the corresponding rate-limiting step of this pathway is the hydrogenation of the O-2 with a reaction barrier of 0.52 eV and an exothermic reaction energy of 0.64 eV. In summary, the preferable path of the hydrogenation reactions of O-2 on TiN4-Graphene is O-2(ads)+H(ads)-> OOH ((ads))-> O+OH(ads). Current results may be benefitial to the design of new electrocatalyst materials based on graphene.