Catalysis on Wide-Band-Gap Semiconductors

Abstract

This paper presents two novel models of catalysis on wide-band-gap semiconductors: injection of electrons (holes) into the conduction (valence) band by donor (acceptor) intermediates and extraction of electrons (holes) by acceptor intermediates in concurrence, while the catalytic surface reaction via ionic intermediates is in progress. At the stationary state of catalysis, the two concurrent rates of charge transfer are assumed exactly equal in magnitude so that conservation of charges are maintained. The models of catalysis provide an interpretation of the variation in catalytic activity with the surface potential of an extrinsic semiconductor induced by an external electrostatic field, and of the variation in apparent activation energy with the bulk potential. Moreover, this theory sheds light on the complexity and the significance of catalytic experiments carried out under dynamic conditions.