Platinum/titanium dioxide catalysts. A photoconductivity study of electron transfer from the ultraviolet-illuminated support to the metal and of the influence of hydrogen
- 1 January 1983
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 79 (3) , 651-660
- https://doi.org/10.1039/f19837900651
Abstract
Photoconductivity measurements have been carried out for a series of powder Pt/TiO2 catalysts containing from 0.05 to 10 wt% Pt as well homodispersed particles (mean diameter ca. 2 nm). The presence of platinum, at least for contents ca. 1 wt%, caused a decrease in the anatase photoconductance σeq at equilibrium under vacuum and this decrease was more pronounced for the highest loadings (5 and 10 wt%). In addition, differences in the times required to reach the steady state were observed, and an attenuation of the u.v. light flux lowered σeq of the Pt-loaded samples, whereas it did not affect that of TiO2 alone. These phenomena can be rationalized in terms of electron transfer from the titania to the platinum. Accordingly, the existence of such a withdrawal by small metal crystallites is substantiated. Conversely, in H2 the Pt deposits decreased the resistance of TiO2, illuminated or not, and this is tentatively attributed to a migration of adsorbed hydrogen atoms from Pt to TiO2 where they form OH– ions and release electrons.Keywords
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