The oxygen evolution reaction (OER)-catalyzing activity of transition metal perovskite oxide catalysts depends on the occupancy of the .sigma.-bonding orbital of e.sub.g symmetry parentage of the active cation. Catalysts having preferred values of e.sub.g orbital filling can have a high intrinsic activity for catalysis of the OER.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with government support under Grant No. DE-FG02-05ER15728, awarded by the Department of Energy. The government has certain rights in this invention.