Electronic structure and orientation of dioxygen species on the surface of CoO-MgO solid solutions

The adsorption of oxygen on the surface of COO-MgO solid solutions was studied by EPR spectroscopy using 170-enriched oxygen. The spin Hamiltonian parameters, geometry, and electronic structure of adsorbed oxygen were discussed. The comparative analysis of the experimental and calculated hf structure evidenced two main forms of adsorbed dioxygen: one with nonequivalent nuclei (end-on bent structure), bonded reversibly at room temperature to surface cobalt ion, and another with equivalent nuclei (side-on structure) stabilized electrostatically and irreversibly on Mg2+ at room temperature. The contribution of electron delocalization and spin polarization to the hf structure was discussed. Significant electron transfer indicates that the C0-02 system is best described as a Co3+-02- adduct in the case of CoO-MgO solid solutions.