Morphology-controllable synthesis of MnO2 hollow nanospheres and their supercapacitive performance

Abstract

Uniform MnO₂ hollow nanospheres with hierarchical (urchin-like and flower-like) and non-hierarchical structures have been synthesized via a dual-template assisted hydrothermal process. The morphology control of the MnO₂ hollow spheres can be easily achieved by altering the mass ratio of Pluronic F-127 to silica spheres. Material characterizations reveal that urchin-like hollow spheres possess the highest BET surface area of 233.4 m² g⁻¹ among the diverse morphologies. A possible formation mechanism for the MnO₂ hollow spheres with different morphologies is proposed. The supercapacitive performance of the MnO₂ spheres was investigated by cyclic voltammetry and galvanostatic charge–discharge techniques. The urchin-like hollow spheres exhibit the highest specific capacitance of 266.6 F g⁻¹ within the potential range of 0–1.0 V. The relationship between the specific capacitance and the morphology of the MnO₂ hollow spheres is also discussed. The good capacitive behavior and cycling stability of the hierarchical MnO₂ hollow spheres highlights the importance of the morphological design and control of materials in practical supercapacitor applications.