CHARACTERIZATION OF PHOTOREDUCED PT TIO2 AND DECOMPOSITION OF DICHLOROACETIC ACID OVER PHOTOREDUCED PT/TIO2 CATALYSTS/

The effect of photoreduction on the properties of Pt/TiO2 catalysts wa s investigated. A decrease of the white-line area in the XANES spectra of Pt/TiO2 catalysts at the Pt L-III edge was observed with increasin g photoreduction time, which denoted the photoreduction of Pt/TiO2 wit h UV illumination. From the EXAFS fitting results, the growth of Pt pa rticles with the photoreduction time could be monitored. The XPS spect ra of Pt/TiO2 catalysts at the Pt4f(5/2) and Pt4f(7/2) bands showed th e presence of Pt-0 and Pt2+ states after photoreduction and the fracti on of metallic Pt-6 was increased with increasing photoreduction time. The optimum photoreduction time for DCA (dichloroacetic acid) decompo sition was 6 h. The partially reduced state of Pt seems to be effectiv e to obtain a high quantum yield in DCA decomposition with minimizing the agglomeration of Pt clusters on the TiO2 surface. (C) 1997 Elsevie r Science B.V.