First principles study of oxygen adsorption on nickel-doped graphite

Abstract

Density functional theory is used in a spin-polarized plane wave pseudopotential implementation to investigate molecular oxygen adsorption and dissociation on graphite and nickel-doped graphite surfaces. Molecular oxygen physisorbs on graphite surface retaining its magnetic property. The calculated adsorption energy is consistent with the experimental value of −0.1 eV. It is found that substituting a carbon atom of the graphite surface by a single doping nickel atom (2.8% content) makes the surface active for oxygen chemisorption. It is found that the molecular oxygen never adsorbs on doping nickel atom while it adsorbs and dissociates spontaneously into atomic oxygens on the carbon atoms which are bound to the nickel. The adsorption energy of −1.4 eV and zero activation energy barrier indicate that O2 dissociative adsorption is both thermodynamically and kinetically favoured over the surface. The large electric field near the doping nickel atom along with the excess electrons on the neighbouring carbon atoms, which are bound to the nickel induce molecular oxygen to adsorb and dissociate favourably.