TEM analysis of Pt-particles embedded on TiO2 exhibiting high photocatalytic activity

Fine particles of semiconductive rutile TiO2 supporting ultra-fine-particle s of Pt were studied by high-resolution analytical electron microscopy. The embedded Pt particles were prepared by decomposing a colloidal organic-Pt complex. This particle system is known to exhibit remarkably high photocata lytic activities. In this study, the structural aspects of the high photoac tivity were examined by high-resolution imaging, X-ray mapping by energy di spersive spectroscopy and electron energy-loss spectroscopy. As a result, t he ultra-fine particles are composed only of Pt and their size distribution is narrow with a mean diameter of 3 nm. The Pt particles with nm-sizes wer e found to grow epitaxially on rutile TiO2 having the following crystallogr aphic relationship; [110] (001)(Pt) // [001] (110)(TiO2). This result suppo rts the expected mechanism that the photo-excited electrons efficiently tra nsfer from TiO2 to Pt and promote the reduction of O-2 to O-2(-) ions which will be able to react with organic molecules at the surface.