The effect of metals located near titanium dioxide domains on photocatalysis 

 

Y. Paz

Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa 32000 Israel

Tel: +972-4-8292486, Fax: +972-4-8230476, Email: paz@tx.technion.ac.il

 

Titanium dioxide is a well-known photocatalyst for water and air treatment as well as for catalytic production of gases. The general scheme for the photocatalytic destruction of organics begins with its excitation by suprabandgap photons, and continues through redox reactions where OH radicals, formed on the photocatalyst surface, play a major role.

            The presence of gold and platinum in the vicinity of titanium dioxide was found to improve the performance of the photocatalyst.  This effect was attributed to a better charge separation between the photoinduced charge carriers and to an ability of the metal to prevent the deactivation of the photocatalyst, probably by a spillover mechanism that supplies oxygen to the TiO₂ surface.

In this presentation, well-defined structures, comprised of alternating micro-stripes of TiO₂ and metal (gold, platinum, or aluminum) and covered with self-assembled monolayers (SAMs) are used to study the effect of the metals on the photodegradation rate of the monolayers.  In contrast to the above mentioned literature, it was found that under certain conditions, not only that the presence of a metal in the vicinity of the photocatalyst does not increase its photoefficiency, but in fact reduces it significantly.  This effect depends to large extent on the size of the metal islands, as well as on other morophological and experimental attributes. The origins and prospects of these phenomena will be discussed.