Abstract
Pt-Re/TiO 2 (R: rutile) and Pt-Re/ZrO 2 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 TiO 2 (R)-supported catalysts, TEM micrographs showed that Pt dispersion increased by Re addition to Pt/TiO 2 (R). XPS spectra indicated that the electronic interaction between Pt and Re on the TiO 2-supported catalysts is stronger than that on the ZrO 2-supported catalysts, and that the state of Re was stable on Pt-Re/TiO 2 (R) under the LT-WGS conditions. These results indicate that one of reasons for the superior catalytic activity of Pt-Re/TiO 2 (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 ZrO 2-supported catalysts, TEM micrographs showed that the Pt dispersion decreased by Re addition to Pt/ZrO 2. XPS spectra indicated that the interaction between Re and support on Pt-Re/ZrO 2 catalysts is stronger than that on Pt-Re/TiO 2 (R), and that the redox reaction between Re 4+ and Re 7+ was repeated on Pt-Re/ZrO 2 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/ZrO 2 catalyst, although Pt-Re/ZrO 2 had lower Pt dispersion than Pt/ZrO 2. Therefore, it was determined that the additive effect of Re on Pt dispersion and catalytic activity was largely affected by the state of Re.
Published Version
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