Kinetics of oxygen removal from ceria

The kinetics of oxygen removal from CeO₂ were investigated using thermogravimetric analysis, at high temperatures, under a reducing atmosphere of Ar–6%H₂. A chemical diffusivity model was developed that takes into account the composition dependence of both the pre-exponential factor and the activation energy. In this model, the pre-exponential factor is given by D₀ =22.32 exp(-0.22x) (cm²/s), and the activation energy is ΔE = 195.4-173.9x (kJ/mol), where x is the nonstoichiometry coefficient in CeO_2-x. The model describes well the oxygen removal kinetics for the entire time range (100 min), demonstrating its superiority over two popular mathematical models that can only fit part of the experimental data.