Photooxidation of M(CO)(6) (M=Mo, W) adsorbed on TiO2

Photooxidation of M(CO)(6) (M = Mo, W) adsorbed on TiO2 has been conducted from a viewpoint of the kinetics and mechanism of the reaction and the photocatalytic effect of TiO2. The reaction rate was first order with respect to the surface concentration of M(CO)(6) and zero order with respect to oxygen pressure. The photocatalytic effect of TiO, was suggested by the fact that the reaction rate of the W(CO)(6)/TiO2 system was considerably greater than that of W(CO)(6)/NaY zeolite. The rate constant strongly depended on the TiO2 employed and was delineated to a direct-allowed band-gap of the TiO2. The photocatalytic effects of TiO2 are tentatively suggested to result from a strongly enhanced decarbonylation of M(CO)(6) by photoinduced valence band holes, followed by rapid reactions with anionic surface oxygen species.