Thin Film Models of SMSI (Show Strong Metal-Support Interactions) Catalysts: Pt on Oxidized Titanium

摘要

Thin films of Pt, vapor deposited on an oxidized Ti foil, have been utilized as models of high surface area Pt/TiO2 catalysts which show strong metal-support interactions (SMSI). Both fully oxidized (Ti(4+)) and partially reduced (significant amounts of Ti(3+)) surfaces were studied. As a function of Pt coverage, the development of bulk Pt chemisorption characteristics occurs at significantly lower coverages on the oxidized substrate. In particular, at a given Pt coverage there is less chemisorption of both CO and H2 on the reduced, a compared to the oxidized, TiO2 and the desorption spectra peak at lower temperatures. No evidence for significant differences in the chemical state of the Pt is found by XPS and AES. We propose a model, consistent with earlier work on high surface area Pt/TiO2 catalysts, in which the morphology of the Pt on the reduced catalysts is significantly flatter (dominated by (111) terraces) and is slightly modified electronically, as compared to the oxidized sample.