PNNL

Abstract

A CeO2-supported Pt catalyst (denoted as Pt/CeO2(800)) was prepared by pre-calcining a commercial CeO2 support at high temperature (800 ºC) before loading Pt via incipient wetness impregnation method. Pt/CeO2(800) exhibits enhanced redox and hydrocarbon (HC) oxidation activity, in comparison to catalyst with untreated CeO2 support (denoted as Pt/CeO2(UT)). Combination of multiple characterization, 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 on 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 in catalytic oxidation of various HC fuel blendstocks with different functionalities (C=C, C-O, and C=O 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) than 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.