Adsorption of O2 on the CaO and SrO (1 0 0) surfaces: A first-principles study

First-principles calculations based on density functional theory (DFT) have been performed to investigate the adsorption of O2 on the CaO and SrO (1 0 0) surfaces. The present results indicate that the bridge-top site for both the CaO and SrO (1 0 0) surfaces is the most favorable site for O2 adsorption, with predicted adsorption energies of 1.437 eV and 1.236 eV, respectively. Detailed analysis of density of states, Mullikan population and vibration frequency are performed. The calculated results imply the possible formation of a peroxo (O22−) when O2 is adsorbed with the bridge-top mode on both CaO and SrO (1 0 0) surfaces.