Synergistic Effects of VOx–Pt Probed by the Oxidation of Propane on VOx/Pt(111)

Abstract

VO(x)/Pt(111), which was grown layer-by-layer and exhibited a well-defined structure, was used as a model catalytic surface to study the intrinsic catalytic activity of Pt, as well as the effect of VO(x) additive, for the oxidation of propane. A special sample system was designed to ensure a reliable analysis of the trace amount of model catalytic reaction products. The results show that the catalytic activities for the oxidation of C3H8 on the Pt(111) surface as adding VO(x) are suppressed apparently at temperatures below 400 K, but enhanced significantly at temperatures above 400 K. Maximum reaction rates are achieved at a VO(x) coverage of about 0.3 ML at the test temperatures of 423 and 473 K. The infrared reflection-absorption spectroscopy (IRAS) results show that the redox property of the VO(x)-Pt is much better than that of the bulklike VO(x). This is confirmed by CO poisoning tests, in that the oxidation of VO(x)/Pt(111) is significantly suppressed by the coadsorbed CO. The kinetic data demonstrate that there are at least two catalytically active sites, metallic Pt and VO(x)-Pt interface, for the activation and oxidation of C3H8. The promotion effects of VO(x) on Pt for the oxidation of C3H8 can be attributed to the synergy between VO(x) and Pt.