Effects of high-temperature CeO2 calcination on the activity of Pt/CeO2 catalysts for oxidation of unburned hydrocarbon fuels

Abstract

A CeO₂-supported Pt catalyst (denoted Pt/CeO₂(800)) was prepared by pre-calcining a commercial CeO₂ support at high temperature (800 °C) before loading Pt via the incipient wetness impregnation method. Pt/CeO₂(800) exhibits enhanced redox and hydrocarbon (HC) oxidation activity, in comparison to a catalyst with untreated CeO₂ support (denoted Pt/CeO₂(UT)). A combination of multiple characterization techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), CO temperature-programed reduction (CO-TPR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), shows that the promoted redox activity of Pt/CeO₂(800) is independent of the morphology of Pt clusters. Instead, it is associated with the enhanced mobility of surface lattice oxygen on the high temperature pretreated CeO₂ support. The catalysts were evaluated for the catalytic oxidation of various HC fuel blendstocks with different functionalities (CC, C–O, and CO bonds) under different simplified and simulated exhaust conditions (with 0.74% and 10% O₂). Under simulated exhaust conditions, fuel molecules, regardless of functionalities, are always more active under lean (high O₂) conditions than under rich (low O₂) conditions although their oxidation reactivity is suppressed by the competitive adsorption of NO and CO. The high redox activity of Pt/CeO₂(800) facilitates the HC oxidation by accelerating the rate-limiting O₂ activation step and broadening the operation window for an oxygen-dominant Pt surface.