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.