First-principles Study Of The Oxygen Adsorption And Dissociation On Graphene For Li-air Batteries

Based on Density Functional Theory, the oxygen adsorption and dissociation ongraphene are studied in this thesis.Graphene can work with rather good performance as Li-air battery electrode,suggesting that graphene itself can be served as catalyst for O₂dissociation reaction.In this work, from first-principles, O₂molecule physical adsorption, O atom chemicaladsorption and O₂molecule dissociation on the graphene are studied. It shows that O₂molecule prefers to stay parallel to the graphene basin plane with the bond length of1.263, which is slightly larger than that of a free O₂molecule（1.235） in vacuum.It is found that charge transfer occurs between the O₂molecule and the graphene sheet,which makes the adsorption energetically stable. The O₂molecule dissociation pathon graphene is optimized by the CNEB method. The energy barrier of the dissociationreaction is2.39eV, which is much smaller than the O₂binding energy（4.30eV）.Results show that graphene has catalytic effect to the O₂dissociation. The O₂molecule adsorption on nitrogen doped graphene is simulated. When the O₂moleculeis physically adsorbed on the N-doped graphene, the bond length of O₂is1.280,and the energy barrier of dissociation reaction decreased to the1.20eV, which showthat nitrogen doping enhance the catalytic effect to the O₂molecule reduction.