In situ investigation of the photocatalytic decomposition of NO on the Ti-HMS under flow and closed reaction systems

Abstract

Mesoporous materials such as Ti-HMS, prepared at ambient temperature, were studied both under continuous flow and closed reaction systems for the photocatalytic decomposition of NO. The results indicate Ti-HMS to be a good photocatalyst with a continuous reactivity under prolonged irradiation. The direct decomposition of NO into N₂, O₂, and N₂O at 275 K with a high selectivity for N₂ and O₂ in a closed system is noteworthy. In situ photoluminescence and EXAFS investigations show that the Ti exists in a tetrahedral coordination and is highly dispersed within the mesoporous material. The TPD studies, before and after the photocatalytic investigations, clearly indicate that NO molecules cannot be adsorb strongly on the surface of Ti-HMS photocatalysts, in contrast to the powdered TiO₂ photocatalysts, where strong NO adsorption species have been observed. It is likely that the charge transfer excited state of the tetrahedrally coordinated titanium oxide species plays a significant role in the direct decomposition of NO.