ANALYTICAL TEM STUDY OF THE SELECTIVE PHOTOCATALYTIC DEPOSITION OF PLATINUM ON TITANIA SILICA MIXTURES AND SILICA-SUPPORTED TITANIA

The photocatalytic deposition of platinum on titania was used to investigate the selectivity of the deposition of metal in the case of a multiphase support. Two kinds of supports were chosen: a mechanical mixture of TiO2 and SiO2 and a silica-supported titania. In both cases, the photodeposition of platinum corresponding to 1 wt% Pt was complete. For the mechanical mixture of TiO2 and SiO2, analytical transmission electron microscopy investigation revealed that platinum was deposited exclusively on titania. The chemical deposition of titania on spherical particles of silica gave small TiO2 particles of 3-5 nm mean size. Raman spectroscopy indicated that deposited TiO2 exhibits the anatase structure. As in the preceding case, platinum was photodeposited exclusively on supported titania particles. This was confirmed by TEM and EDX analyses. This method of metal deposition could be used to decorate a multicomponent support with a noble metal, the metal being exclusively deposited on the photosensitive parts or constituents. It represents a possible method of preparing a metal catalyst deposited on a highly divided supported support. © 1990.