Characterization of a Pt/TiO2 (rutile) catalyst for water gas shift reaction at low-temperature

Recently, we have reported that the Pt/TiO2 (R: rutile) catalyst has relatively high activity for the water gas shift reaction at low-temperature (LT-WGS). In this study, Pt catalysts supported on TiO2 (R), TiO2 (A: anatase), ZrO2 and Al2O3, were characterized by TEM, XPS, TPD, and FT-IR measurements. These results suggested detailed reasons for the high catalytic activity of the Pt/TiO2 (R) catalyst. TEM micrographs showed that the Pt dispersion of the Pt/TiO2 (R) catalyst was lower than those of the Pt/ZrO2 and Pt/Al2O3 catalysts, although Pt/TiO2 (R) had superior catalytic activity. Furthermore, the Pt/TiO2 (R) catalyst had larger Pt dispersion than Pt/TiO2 (A), although Pt/TiO2 (R) had lower BET surface area than Pt/TiO2 (A). XPS spectra indicated that the TiO2 (R and A) supports had a stronger electronic effect with Pt than ZrO2 and Al2O3. In addition, CO-TPD profiles revealed that the strength of Pt–CO bonding on Pt/TiO2 (R) and Pt/TiO2 (A) catalysts was weakened due to the interaction between the support and Pt. These results indicated that the catalytic activity of Pt catalysts for LT-WGS is greatly affected by the interaction between the support and Pt, rather than by Pt dispersion, although the difference in catalytic activity between the Pt/TiO2 (R) and Pt/TiO2 (A) catalysts can mainly be explained by the degree of Pt dispersion.Finally, IR spectra of CO–H2O and –D2O reactions on the Pt catalysts indicated that the high catalytic activity of Pt/TiO2 (R) could be attributed to the fast formation and decomposition of formate as a reaction intermediate.