Search

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. [ABSTRACT FROM AUTHOR]

The formation of large crystals in an anode during the working cycle is harmful to the lithium-ion battery's capacity and cycling performance. However, the underlying mechanism is not clearly revealed, which significantly hinders the development of strategies to suppress the formation of large particles. Here, we studied the formation mechanism of large crystals with the assistance of electron beam irradiation. The large crystal formed after the lithiation of SnO2 was identified as Li4.4Sn. The formation of such large Li4.4Sn is significantly promoted by the high Li+ concentration in the sample, which contributes to the formation of more Li4.4Sn/Li2O interfaces. Within the Li+ supersaturation environment, a considerable number of Li4.4Sn nanocrystals with larger size are formed. Theoretical calculation results revealed that the Li4.4Sn/Li2O interface is unstable, which thus drives the aggregation of Li4.4Sn nanocrystals. Moreover, by reducing the Li+ concentration and the size of SnO2 below 15 nm, the formation of large Li4.4Sn crystals can be effectively suppressed. This work reveals the formation mechanism of large crystals in lithiated SnO2, which may supply enlightening insights into the structural engineering of tin-based anode materials. [ABSTRACT FROM AUTHOR]