Parameters influencing photoassisted adsorption of NO on TiO2 powder

The use of semiconductor materials as photocatalysts for cleaning gas proce sses has received increasing interest in the last decade. In order to make more active catalysts, it is worthwhile to investigate the main processes i nfluencing photocatalytic reactions in more detail. One of these is the pro cess of coadsorption of the reaction components on the catalyst surface und er irradiation. It is shown that photoassisted NO adsorption can serve as a model system in order to investigate the influence of irradiation intensit y and temperature on the adsorption isotherm, respectively. This advantage stems from the fact that NO is a radical, offering the possibility to stabi lize electrons as well as holes on the TiO2 surface. This results in the fo rmation of NO/NO pairs. The proposed adsorption model, however, does not on ly consider this pair formation but, in addition, the adsorption of NO mole cules on charged sites while the complementary charged sites are stabilized by traps present on the surface. The proposed adsorption isotherm is suppo rted by experimental results.