Reduction properties of Ce in CeOx/Pt/Al2O3 catalysts

A controlled surface reaction (CSR) technique has been successfully employed to prepare a series of CeO x modified Pt/Al 2 O 3 catalysts, offering a unique system to specifically probe the relationship between Ce and Pt without any bulk CeO 2 present. Ce L 3 edge X-ray absorption near edge structure (XANES) analysis was used to ascertain the oxidation state of the Ce in the catalyst materials in atmospheres of air, H 2 (g), and CO (g) at room temperature. The XANES data showed that the Ce was present as both Ce 3+ and Ce 4+ oxidation states in an atmosphere of air, becoming predominantly present as Ce 3+ in H 2 and CO. The results indicate the role of Pt in the process, and show that with the absence of bulk CeO 2 , changes in Ce oxidation state can be observed at non-elevated temperatures. The CeO x /Pt/Al 2 O 3 catalysts were tested for their performance toward the water gas shift (WGS) reaction and showed improved performance compared to the unmodified Pt/Al 2 O 3 , even at very low concentrations of Ce (∼0.35 wt-%).