Developing a dynamic oxygen migration-release model for enhanced understanding of Ce-materials reactivity

Abstract

Oxygen atom migration within solid oxides exerts a profound affects material properties, yet a rigorous conceptual framework for quantifying dynamic migration has been absent. To bridge this gap, we have developed a dynamic oxygen migration-release model, employing the differential element method with comprehensive mathematical proof. This novel model elucidates the exponential decay in the oxygen release rate of metal oxides as a function of the liberated oxygen quantity. We refined the model to discern between the migration of interior (bulk) oxygen and the reactions of oxygen at the surface, providing experimental validation for the energy barriers associated with each migration process. Taking CeO₂ as a case study, our model predicted and corroborated the energy barrier for oxygen release under various temperatures and morphologies, aligning with Density Functional Theory (DFT) analysis. Furthermore, the model's versatility is evidenced by its applicability to a wide range of metal oxides, including ceria-zirconia solid solutions, manganese oxide, and iron oxide, suggesting a broad potential for universal application. The unveiled dynamics of oxygen migration and release provide a theoretical foundation for refining the design of functional metal oxides and lay the groundwork for a more precise assessment of their oxygen reactivity.