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