Structure characterization of Pt-Re/TiO2 (rutile) and Pt-Re/ZrO2 catalysts for water gas shift reaction at low-temperature

Pt-Re/TiO2 (R: rutile) and Pt-Re/ZrO2 catalysts, which have superior catalytic activity for the water gas shift reaction at low temperature (LT-WGS), were characterized by TEM and XPS measurements in order to examine the role of Re in enhancing catalytic activity. For the TiO2 (R)supported catalysts, TEM micrographs showed that Pt dispersion increased by Re addition to Pt/TiO2 (R). XPS spectra indicated that the electronic interaction between Pt and Re on the TiO2-supported catalysts is stronger than that on the ZrO2-supported catalysts, and that the state of Re was stable on Pt-Re/TiO2 (R) under the LT-WGS conditions. These results indicate that one of reasons for the superior catalytic activity of Pt-Re/TiO2 (R) catalyst is an increase in Pt dispersion. The stable Re acts as anchors for Pt particles, resulting in high Pt dispersion. On the other hand, for the ZrO2-supported catalysts, TEM micrographs showed that the Pt dispersion decreased by Re addition to Pt/ZrO2. XPS spectra indicated that the interaction between Re and support on Pt-Re/ZrO2 catalysts is stronger than that on Pt-Re/TiO2 (R), and that the redox reaction between Re4+ and Re7+ was repeated on Pt-Re/ZrO2 in the course of the LT-WGS reaction. These results suggested that the Re redox reaction significantly contributes to the high catalytic activity of the Pt-Re/ZrO2 catalyst, although Pt-Re/ZrO2 had lower Pt dispersion than Pt/ZrO2. Therefore, it was determined that the additive effect of Re on Pt dispersion and catalytic activity was largely affected by the state of Re. (c) 2006 Elsevier B.V. All rights reserved.