The Importance of Strongly Bound Pt–CeOx Species for the Water-gas Shift Reaction: Catalyst Activity and Stability Evaluation

We demonstrate ways to prepare active and stable Pt–CeOx catalysts for the water-gas shift reaction (WGSR). Various synthesis protocols are shown to work; the best being the coprecipitation/gelation method, which suppresses the crystal growth of ceria during calcination by the incorporation of some platinum in the bulk oxide. Metallic platinum nanoparticles are not necessary for an active WGSR catalyst. Reaction light-off occurs at ∼120 °C, where Pt2+ species bound to ceria are still present. No activation period, and no hysteresis phenomena were found. During reaction at reducing conditions, some Pt is reduced, but it is reoxidizable. The stability of these low-content (<2 at.%) Pt/CeOx catalysts is high even in realistic reformate gas streams. To avoid cerium(III) hydroxycarbonate formation at room temperature-shutdown with water condensation, a small amount (∼1%) of gaseous oxygen is added to the reaction gas mixture. Cyclic shutdown/startup operation is thus possible without catalyst degradation.