Effect of pH on the incorporation of platinum into the lattice of sol–gel titania phases

Titania and platinum/titania catalysts were prepared by co-gelling titanium ethoxide and platinum acetylacetonate in acid or basic media. For the acid conditions, platinum promoted the formation of rutile; but, when the medium was basic, the samples were a mixture of anatase and rutile. Platinum also affected the titania energy band-gap. The reactivity, for methylcyclohexane dehydrogenation, of the samples prepared in a basic environment, was larger than that for those prepared in an acid medium. The highest effect and the most important modification of the TiO 2 energy band-gap occurred for pH 3, which suggests a large incorporation of platinum into the lattice of titania phases.