A Model for the Temperature-Programmed Reduction of Low and High Surface Area Ceria

This article develops an experimental and theoretical kinetic analysis of ceria reduction using TPR experiments, considering both low and high surface area samples. From data in the existing literature on oxygen diffusion within the ceria lattice, it may be shown that spatial effects within ceria crystallites can be neglected for temperature ranges relevant to ceria reduction without risking significant errors. Moreover, oxygen transport seems not to be responsible for the qualitative changes in TPR profiles occurring on low and high surface area samples. We have developed a simple kinetic model that is able to predict the unimodal and bimodal shape of low and high surface area ceria with correct location of the main peaks. The model displays a satisfactory quantitative agreement with respect to the degree of reduction as a function of temperature. The model highlights the influence of the kinetic and thermodynamic properties of the material and of its textural changes with temperature (sintering). The model can be used to predict the outcome of TPR experiments over a broad range of specific surface areas.