The oxygen adsorption on MnO₂ was studied in the light of quantum chemistry. The bare cluster of MnO₂ with the size of Mn₇O₁₄ was employed to evaluate the difference in the frontier molecular orbital energy, Mulliken population and net charge of MnO₂ three planes, (001), (110) and (111). The embedding cluster of Mn₃O₆＋Ca₇＋1096PCs was used to study the oxygen adsorption on MnO₂. Of three planes (001), (110) and (111) of MnO₂, the plane (110) has the highest HOMO energy. And thus, it is the easiest for electrons to effuse from the plane (110) of MnO₂ and transfer to O₂. The catalytic activity of MnO₂ to the first electron transfer of the oxygen reductive reaction (ORR) increases in the sequence of (001)＜(111)＜(110). The catalytic ability of MnO₂ to the first electron transfer of the ORR was confirmed by the calculations of adsorption energy, O—O bond length, Mulliken overlap population, and net charge on the concerned atoms after O₂ adsorption on MnO₂. The adsorption energy evolved after O₂ adsorption on MnO₂ is much larger than that evolved in reaction O₂＋e^－→O₂^-. It suggests that MnO₂ can strongly catalyze this reaction and thus more energy is evolved as it proceeds on MnO₂. The electron-transfer from MnO₂ to O₂ is a process of delocalization, that is, the one transferred electron is not only from the Mn atom at adsorption site but also from the Mn atoms of the bulk MnO₂ crystal cluster.

Key words: oxygen reduction reaction, metal-air battery, MnO₂, electrocatalysis, ab initio