A bifunctional catalyst for the single-stage water–gas shift reaction in fuel cell applications. Part 2. Roles of the support and promoter on catalyst activity and stability

The nature of oxide supports has a crucial effect on the performance of Pt-based catalysts in the water–gas shift reaction. Supports not only determine the activity of the catalyst, but also influence their stability (deactivation mechanism). Among the catalysts studied, Pt/TiO2 was the most active. Pt/CeO2 deactivated with time due to the formation of stable carbonate on the ceria surface. Sintering of Pt was found to be the cause of Pt/TiO2 deactivation. Using mixed oxides as catalyst supports did not improve the activity despite the better red–ox properties of mixed oxides compared with the single-oxide supports. Pt/TiO2 could be stabilized by adding a second metal (Re), which prevented Pt sintering. In addition, Pt–Re/TiO2 was more active than Pt/TiO2. Under WGS conditions, part of the Re was present in oxidizing form (ReOx); we speculate that this helped improve the catalyst activity.