Unraveling the Catalytic Mechanism of Co3O4 for the Oxygen Evolution Reaction in a Li-O-2 Battery

Unraveling the catalytic mechanism of transition-metal oxides (TMOs) for the charging reaction in a Li-O-2 battery and characterizing their surface structures and electronic structure properties of active sites are of great importance for the development of an effective catalyst to improve low round-trip efficiency and power density. In the current study, an interfacial model is first constructed to study the decomposition reaction mechanism of Li2O2 supported on Co3O4 surfaces. The computational results indicate that the O-rich Co3O4 (111)C with a relatively low surface energy in high O-2 concentration has a high catalytic activity in reducing overpotential and O-2 desorption barrier due to the electron transfer from the Li2O2 layer to the underlying surface. Meanwhile, the basic sites of Co3O4 (110)B surface induce Li2O2 decomposition into Li2O and a dangling Co-O bond, which further leads to a high charging voltage in the subsequent cycles. The calculations for transition-metal (TM)-doped Co3O4 (111) indicate that P-type doping of Co3O4 (111) exhibits significant catalysis in decreasing both charging overpotential and O-2 desorption barrier. The ionization potential of doped TM is determined as an important parameter to regulate the catalytic activity of metal oxides.