Pt-Re/TiO2 (R: Rutile) and Pt-Re/ZrO2 catalysts were characterized by in situ FT-IR and CO-TPD measurements. Results indicated that the strength of the CO bonding was weakened upon addition of Re, meaning that the CO species adsorbed on the catalysts was activated for steam. Further, a linear relationship was identified between the strength of the adsorbed CO and the turn over frequency (TOF) for LT-WGS, except in the case of Pt-Re/ZrO2. Pt-Re/ZrO2 exhibited a higher TOF than that predicted from the strength of the adsorbed CO. This may be due to Re redox reaction. Additionally, in situ FT-IR measurements of CO-H2O and CO-D2O reaction over Pt-Re catalysts were carried out in order to elucidate the details of the reaction mechanism. Results of these investigations indicated that the bidentate formates observed on Pt-Re/TiO2(R) were similar to those on Pt/TiO2(R); the type of formates did not change upon Re addition. On the other hand, the bidentate formates were only observed on Pt-Re/ZrO2, whereas bidentate and bridging-type formates were observed on Pt/ZrO2. These results suggest that the reaction changed upon addition of Re to Pt/ZrO2. (c) 2006 Elsevier B.V. All rights reserved.