Combining in-situ TEM observations and theoretical calculation for revealing the thermal stability of CeO₂ nanoflowers

The thermal stability of CeO₂ nanomaterials can directly impact both the uniformity of the supported catalysts and the catalytic behavior of CeO₂ itself. However, knowledge about the thermal stability of CeO₂ is still deficient. Here, we conduct in-situ transmission electron microscopy experiments and theoretical calculations to elucidate the thermal stability of CeO₂ nanomaterials under different environments. A sinter (< 700 ℃) and a structural decomposition (> 700 ℃) are observed within CeO₂ nanoflowers under O₂. The sinter firstly occurs among the nanoflowers' monomers and then the sintered nanoparticles structurally decompose to tiny nanoparticles from the strain interface. Under a vacuum environment, the CeO₂ nanoflowers firstly undergo a transition from cubic fluorite CeO₂ to hexagonal Ce₂O₃, accompanied by the oxygen release. The Ce₂O₃ nanoparticles further atomically sublimate from the edges to the center under high temperatures. Theoretical calculation results reveal a considerably lower energy barrier for the structural decomposition under O₂ and for the sublimation under vacuum. This work provides a perspective on the structural design and performance optimization of CeO₂-based catalysts.