Influence of Phosphorus Configuration on Electronic Structure and Oxygen Reduction Reactions of Phosphorus-Doped Graphene

Encouraged by the great promise of heteroatoms-doped carbon materials for catalyzing the oxygen reduction reaction (ORR) in fuel cells, phosphorus-doped carbon has exhibited high catalytic activity for the ORR. Here, by means of comprehensive density functional theory (DFT) computations, we explored the relationships among the catalytic activity, stability, and the local chemical bonding states at dopant sites of P-doped graphene sheets for ORR to identify the most optimized P-doped graphene structure. The structures show that the P atom can substitute one or two C atoms to form P-doped graphene structures with three or four P–C bonds (PC3G or PC4G), respectively, and these structures are easily oxidized into the OPC3G and OPC4G models with P–O bond. The further calculations reveal that the stability, band structure, surface charge distribution, potential active sites, and free energy of the rate-determining step of P-doped graphene can be modulated effectively by the chemical bonding states of P atom and the formation of C–P–O bond. The OPC3G model is the most effective and stable P-doped graphene for ORR due to its stability, activity, and the amount of the potential active sites. Another significant finding is that the C atoms possessed high negative charge, which also can be the optimal active sites for ORR. Our work provides useful guidance for the rational design and fabrication of P-doped graphene framework and helpful further activity enhancement.