Manipulating Reaction Rates of Metal-Oxide Heterogeneous Catalysts via Semiconductor Heterojunctions

Heterojunctions of metal oxide semiconductors enable the manipulation of surface chemistry for heterogeneous catalysts or sensors without introducing dopants and their attendant complications. If one of the semiconductors is sufficiently thin, charge exchange between the two semiconductors leads to charge buildup at the free surface. The excess charge influences the Lewis acid-base character of the surface and propagates into properties such as catalytic activity. Although the available literature offers evidence for such effects, published work does not outline a quantitative framework that links heterojunction behavior to catalytic activity. The present work develops and demonstrates such a framework for the oxidation of methanol to formaldehyde with a heterojunction of thin polycrystalline V2O5 grown on polycrystalline anatase TiO2. The framework accurately reproduces activity changes by a factor of 20 in response to V2O5 thickness and TiO2 donor concentration.