Recently, we have reported that the Pt/TiO2 (R: rutile) catalyst has relatively high activity for the water gas shift reaction at low-temperature (LT-WGS). In this study, Pt catalysts supported on TiO2 (R), TiO2 (A: anatase), ZrO2 and Al2O3, were characterized by TEM, XPS, TPD, and FT-IR measurements. These results suggested detailed reasons for the high catalytic activity of the Pt/TiO2 (R) catalyst. TEM micrographs showed that the Pt dispersion of the Pt/TiO2 (R) catalyst was lower than those of the Pt/ZrO2 and Pt/Al2O3 catalysts, although Pt/TiO2 (R) had superior catalytic activity. Furthermore, the Pt/TiO2 (R) catalyst had larger Pt dispersion than Pt/TiO2 (A), although Pt/TiO2 (R) had lower BET surface area than Pt/TiO2 (A). XPS spectra indicated that the TiO2 (R and A) supports had a stronger electronic effect with Pt than ZrO2 and Al2O3. In addition, COTPD profiles revealed that the strength of Pt-CO bonding on Pt/TiO2 (R) and Pt/TiO2 (A) catalysts was weakened due to the interaction between the support and Pt. These results indicated that the catalytic activity of Pt catalysts for LT-WGS is greatly affected by the interaction between the support and Pt, rather than by Pt dispersion, although the difference in catalytic activity between the Pt/TiO2 (R) and Pt/TiO2 (A) catalysts can mainly be explained by the degree of Pt dispersion. Finally, IR spectra of CO-H2O and -D2O reactions on the Pt catalysts indicated that the high catalytic activity of Pt/TiO2 (R) could be attributed to the fast formation and decomposition of formate as a reaction intermediate. (c) 2005 Elsevier B.V. All rights reserved.