Combining in-situ TEM observations and theoretical calculation for revealing the thermal stability of CeO2 nanoflowers
Mingyun Zhu, Kuibo Yin, Yifeng Wen, Shugui Song, Yuwei Xiong, Yunqian Dai, Litao Sun
Abstract
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 °C) and a structural decomposition (> 700 °C) 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.