ELECTRON-MICROSCOPY OF SUPPORTED METAL PARTICLES .1. BEHAVIOR OF PT ON TITANIUM-OXIDE, ALUMINUM-OXIDE, SILICON-OXIDE, AND CARBON

Transmission electron microscopy has been used to investigate the structure and growth characteristics of platinum on thin films of titanium oxide, aluminum oxide, silicon oxide, and carbon. Significant differences in the sintering characteristics of the metal on the various supports was observed after these systems had been treated in hydrogen at temperatures over the range 425 to 1075 °K. Sintering occurred on all supports but the metal dispersion was significantly more stable on titanium oxide than the other supports. Examination of platinum on titanium oxide at high resolution showed that the metal particles were predominately hexagonal in outline, of uniform thickness and very thin, indicating a pill-box morphology. Electron diffraction and lattice spacing measurements showed that the titanium oxide support was reduced to Ti4O7 in the presence of platinum. In the absence of platinum only the rutile form of TiO2 was observed. We conclude that platinum catalyzes the reduction of TiO2 to Ti4O7 and deposits as thin pill-box structures on the surface of the Ti4O7. The unique structural features of the type observed for platinum on titanium oxide was not observed with the other supports, and is believed to result from a strong metal-support interaction. © 1979.