Accession Number : ADA117892

Title :   Properties of Pt Supported on Oxides of Titanium.

Descriptive Note : Technical rept.,


Personal Author(s) : Chen,Bor-Her ; White,J M

PDF Url : ADA117892

Report Date : 09 Jun 1982

Pagination or Media Count : 20

Abstract : Platinum, suppported on TiO2, TiO and Ti2O3 in various forms, has been investigated using a variety of physical and chemical techniques. On H2 pretreated TiO2, on TiO and on Ti2O3 samples (all platinized), SMSI behavior, i.e. limited H2 uptake, was noted. Very fast H-for-D exchange rates were observed for H2D2 mixtures on all these materials indicating that dissociative adsorption still occurs readily. Using XPS, SAES, TEM and STEM data we conclude that surface contamination, diffusion of Pt into the bulk oxide, Formation of surface mixed metal oxides and metal agglomeration are not significant contributors to the observed loss of H2 uptake capacity. On the basis of qualitative bulk electrical conductivity data and XPS data, we suggest that the SMSI effect is best understood in terms of a bulk oxide reduction model. In this model, bulk conduction band electrons tunnel readily through a thin TiO2 layer at the surface to reach Pt particles where they are trapped and furnish a negatively charged Pt particle with good capacity for dissociating H2 but weak binding of atoms. (Author)

Descriptors :   *Platinum, *Titanium oxides, *Titanium dioxide, *Hydrogen, *Deuterium, *Surface chemistry, Catalysts, Dissociation, Adsorption, Chemisorption, Electrons, Anions

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE