Ce Defect Diffusion in Ceria Using Defects Chemical Calculation and Density Functional Theory

CeO₂ shows high oxygen storage/release capacity (OSC) due to its aliovalancy between +3 and +4 as functions of temperature and oxygen partial pressure. Addition of Zr in CeO₂ enhances the OSC further, and recently Ce_0.75Zr_0.25O₂ (CZO) has been studied for anode support of solid oxide fuel cell. However, Zr and Ce in CZO have been reported to be separated under reduction.<br/>Since the phase separation occurs through the constituents’ diffusion, we studied Ce defects diffusion to understand the main defect for the phase separation. Ce defects are the main focus, as a rate-limiting element, because oxygen is a well-known fast diffusion element. Several defect concentrations in CeO₂ are calculated for diffusion coefficient by using defects chemical calculation. Migration enthalpy of Ce vacancy and interstitial is calculated by using NEB method with consideration of oxygen vacancy clustering effect. Ce interstitial with an oxygen vacancy is found to be the main diffusion element under oxidation and reduction, contradicting a recent article [1].<br/><br/>[1] Stefan Beschnitt et al., J. Physical Chemistry, 27307 (2015).