A perovskite oxide optimized for oxygen evolution catalysis from molecular orbital principles

The efficiency of many energy storage technologies, such as rechargeable metal-air batteries and hydrogen production from water splitting, is limited by the slow kinetics of the oxygen evolution reaction (OER). We found that Ba _0.5Sr_0.5Co_0.8Fe_0.2O _3-δ (BSCF) catalyzes the OER with intrinsic activity that is at least an order of magnitude higher than that of the state-of-the-art iridium oxide catalyst in alkaline media. The high activity of BSCF was predicted from a design principle established by systematic examination of more than 10 transition metal oxides, which showed that the intrinsic OER activity exhibits a volcano-shaped dependence on the occupancy of the 3d electron with an e _g symmetry of surface transition metal cations in an oxide. The peak OER activity was predicted to be at an e_g occupancy close to unity, with high covalency of transition metal-oxygen bonds.