Phase transformation of hierarchical nanobranch structure from SnO to SnO2 and its electrochemical capacitance

Hierarchical SnO2 core–shell nanobranches are produced by thermal oxidization of hierarchical SnO nanobranches that are synthesized using a vapor transport method. The SnO nanobranches with a single crystalline tetragonal structure were heat-treated at 923 K in an ambient atmosphere and completely transformed to hierarchical SnO2 nanobranches with an orthorhombic crystal structure. The SnO2 nanobranches of a polymorphism have a core–shell structure in which SnO2 phase (P212121) is formed in the core and SnO2 phase (Pbcn) at the shell. The electrochemical capacitive properties of the SnO2 nanobranches are evaluated by cyclic voltammograms and galvanostatic charge–discharge measurements. Results show that the hierarchical SnO2 nanobranches have an excellent pseudocapacitive performance, i.e., the maximum specific capacitance of 40.5 μF/cm2 and long-term cycling stability up to 1000 cycles with the 8.9% loss of maximum specific capacitance.

► SnO nanobranches were transformed to hierarchical SnO2 nanobranches. ► The SnO2 nanobranches have a core–shell structure with SnO2 (P212121) and SnO2 (Pbcn). ► The hierarchical SnO2 core–shell nanobranches have long-term stability up to 1000 cycles.