The in-situ characterization of titanium oxides prepared in the zeolite cavities and framework and their photocatalytic reactivities for the direct decomposition of NO into N-2 at 275K.

The photoluminescence, ESR and XAFS (XANES and FT-EXAFS) investigations of the various types of Ti-oxide catalysts prepared on and in zeolites indicate that the Ti-oxide/Y-zeolite catalyst prepared by an ion-exchange method and the Ti-silicalite catalyst consist of titanium oxide moieties having a tetrahedral coordination. These Ti-oxide/Y-zeolite and Ti-silicalite catalysts show a high photocatalytic reactivity and selectivity to produce N-2 in the direct decomposition of NO molecules at 275 K. On the other hand, the catalysts which involve the aggregated octahedrally coordinated titanium oxide species and the bulk powdered TiO2 catalyst show a low selectivity for the formation of N-2 in the photocatalytic decomposition of NO and produce N2O selectively in place of N-2. The in situ photoluminescence, ESR and XAFS studies indicate that the charge transfer excited state of tetrahedrally coordinated Ti-oxide species play a significant role in the direct photocatalytic decomposition of NO into N-2 and O-2.