Oxidation and Reduction Reaction Kinetics of Mixed Cerium Zirconium Oxides

Abstract

The oxidation and reduction of mixed cerium zirconium oxides, Ce1–xZrxO2, with x varied in the range 0–0.3 in steps of 0.05, in a low-pressure oxygen atmosphere were experimentally investigated. The experiments utilized a novel method developed by the authors, in which the samples are reduced and oxidized in a sealed vacuum chamber by irradiating them with a xenon arc lamp. The changes in pressure due to the release or consumption of oxygen are used to quantify the extent and rates of the reactions. The system can achieve heating rates in excess of 100 °C s–1, which is hundreds of times faster than is possible with a thermobalance. In addition, the gas phase transport is very rapid as it is driven by pressure gradients. The combined high heating rate and fast gas phase transport offers unique conditions in which to measure the actual kinetics of the reactions. The oxidation kinetics showed a strong dependence on the amount of Zr4+ in the samples, where the rate of oxidation decreased with increasing Zr4+ ...