Reduction properties of Ce in CeOx/Pt/Al2O3 catalysts

Abstract

Abstract A controlled surface reaction (CSR) technique has been successfully employed to prepare a series of CeOx modified Pt/Al2O3 catalysts, offering a unique system to specifically probe the relationship between Ce and Pt without any bulk CeO2 present. Ce L3 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, H2 (g), and CO (g) at room temperature. The XANES data showed that the Ce was present as both Ce3+ and Ce4+ oxidation states in an atmosphere of air, becoming predominantly present as Ce3+ in H2 and CO. The results indicate the role of Pt in the process, and show that with the absence of bulk CeO2, changes in Ce oxidation state can be observed at non-elevated temperatures. The CeOx/Pt/Al2O3 catalysts were tested for their performance toward the water gas shift (WGS) reaction and showed improved performance compared to the unmodified Pt/Al2O3, even at very low concentrations of Ce (∼0.35 wt-%).