Effect of illumination on the adsorptive power and catalytic activity of a semiconductor

Abstract

1. On the basis of the general ideas of the electron theory of chemosorption and catalysis it was shown that the adsorptive power of a surface and at the same time the reactivity of adsorbed particles depends on the relative amount of “strong” and “weak” chemosorption forms on the surface and under otherwise equal conditions, this in its turn is determined by the concentration of the electron and hole gas on the crystal surface. 2. A change in this concentration under the action of illumination leads to a change in the relative content of the chemosorption form and thus to a change in the adsorptive power and catalytic activity of a semiconductor. In other words, the action of light may be reduced to a change in the concentration of surface free valences, responsible for chemosorption and leading to the catalytic process. 3. The relative change in the adsorptive power is expressed in terms of the relative changes in concentration of electron and hole gases on the crystal surface. Criteria for photoadsorption have been established. The problem of the effect of illumination on the reactivity of adsorbed particles has been examined.