An activity descriptor for perovskite oxides in catalysis

Perovskite oxides are a class of important metal oxide catalysts, the activities of which are explained largely by the delocalized band descriptor and the local orbital descriptor that are fundamentally debated. We solve this dispute by proposing a frontier band orbital descriptor that rationalizes catalytic activity trends over a series of perovskite oxides. The descriptor is defined as the energy difference (Δε) between the highest occupied band orbital and the lowest unoccupied band orbital, as determined by using valence-band X-ray photoelectron spectroscopy and O K-edge X-ray absorption spectroscopy, respectively. Catalytic activity in CO or NO oxidation increases linearly as Δε value decreases, evidencing the validity of the descriptor. Owing to the frontier orbitals of catalytic sites being endowed with characteristics of delocalized bands of entire catalysts, this descriptor gives unified explanations to disparate reported results, providing a promising strategy for designing optimal semiconducting metal oxide catalysts, particularly for perovskite catalysts.