Abstract
The mechanism of oxygen reduction reaction for surfur-doped graphene catalyst was investigated by first-principles calculation. Several parameters, such geometry structure, reaction energy and electronic structure were used to analyze the reaction process. The results show that the OOH molecule absorbed on S-graphene with pyridine structure exhibits chemical adsorption. But the OOH molecule on S-graphene with pyrrole structure performs physical adsorption. The adsorbed energies of OOH molecule on S-graphene prove such phenomenon. The electronic structure shows that the excellent ORR of OOH molecule on S-graphene with pyridine structure comes from their adjacent energy level of valence electron no matter in highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO).
Highlights
Reported by Zhang et al[9], two sulfur hybridized graphene sheets (C61H19S and C60H18S) were built with pyridine and pyrrole species as shown in Fig.1, respectively
A molecular orbital package based on the density functional theory (DFT) is adopted to calculate the oxygen reduction reaction (ORR) process and electronic structures of graphene doping with sulfur
When another H atom was introduced into the system, the reaction energies of S-graphene with pyridine structure are equal to -0.7377eV, -1.4313eV, and -2.0575eV for each reaction steps respectively, wherein the corresponding reaction energies are equal to -0.6792eV, -1.9017 eV, and -2.4523eV for S-graphene with pyrrole (Fig.3(b))
Summary
Reported by Zhang et al[9], two sulfur hybridized graphene sheets (C61H19S and C60H18S) were built with pyridine and pyrrole species as shown in Fig., respectively. A molecular orbital package based on the density functional theory (DFT) is adopted to calculate the oxygen reduction reaction (ORR) process and electronic structures of graphene doping with sulfur. The ORR process of pure graphene and the other less efficient two-step two-electron pathway in which hydrogen peroxide was formed as an intermediate, O2+2H++2e-→H2O2, were not considered anymore. All of these impurity graphene models were relaxed to arrive at its global minimum energy. The calculation of total energy and electronic structure was followed by the geometry optimization with Selfconsistent field (SCF) tolerance of 2 x 10-5 au/atom
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