The influence of platinum on UV and ‘visible’ photocatalysis by rutile and Degussa P25

The influence of platinum on the UV photocatalytic degradation of dichloroacetate anion (DCA) by a high area rutile and by the, mainly anatase, P25 form of TiO2 has been compared. Platinum was deposited photochemically and Pt(II) was generally more active than Pt(0) but the differences were small. Although the catalytic activity of rutile was much less than that of the P25, the effect of platinum addition was so much greater on rutile than on P25 that the activities of the Pt treated titanias were similar. Charge carrier separation by platinum is probably much more significant on rutile than on P25.Neither the platinum-free catalysts nor any of the Pt/P25 catalysts oxidized DCA when excited by ‘visible’ radiation (λmax = 435 and 490 nm). However, ‘visible’ light irradiation of Pt/rutile did oxidize DCA. Visible light photocatalysis by Pt/rutile was over three times faster than UV photocatalysis by untreated rutile powder. This suggests that electron trapping by Pt/rutile allows effective utilization of the small 405 nm component emitted by ‘visible’ radiation sources.