The strong interaction between Pt and TiO2 under oxidizing atmosphere was studied by means of X-ray photoelectron spectroscopy (XPS) and Ar+ sputtering test. The results obtained show that under oxidizing atmosphere Pt-0 atoms can thermally diffuse into TiO2 lattice and be oxidized to Pt2+ to substitute for Ti4+ or form the interstitial ions at 673 K. (c) 2004 Elsevier B.V. All rights reserved.