Water-gas-shift reactions over Ir/TiO2 and Ir-Re/TiO2 catalysts were studied, employing a closed gas circulation system. Addition of Re to Ir/ TiO2 catalysts clearly accelerated the WGS reaction, as is in the cases of our previous study over Pt/TiO2 and Pd/TiO2 catalysts. The FT-IR analyses of the adsorbed species during the reaction exhibited the enhancement of the adsorbed CO peaks in the lower wavenumber region with the increase of Re content. These peaks are supposed to be the adsorbed CO neighboring to the adsorbed OH function, which was formed by the dissociation of water on the Re metal or ReOx species of Ir-Re/TiO2 catalysts. (c) 2006 Elsevier B.V. All rights reserved.