Controllable synthesis of different microstructured MnO2 by a facile hydrothermal method for supercapacitors

Different microstructured MnO2 was synthesized as a pseudocapacitive material by using a facile hydrothermal method. MnSO4·H2O and (NH4)2S2O8 were reacted at 120 °C for 12 h to form MnO2, for which the morphology and phase composition of the MnO2 formed could be well controlled. The obtained MnO2 samples were comparatively characterized in terms of their crystallographic structure, microstructure and electrochemical performance. The results revealed that the MnO2 was controllably formed in different microstructures (nanorod, hollow urchin and smooth ball) with different crystalline phase compositions. The average specific capacitance of MnO2 nanorod, hollow urchin and smooth ball at a scan rate of 5 mV/s was 317, 204 and 276 F/g, respectively, indicating that MnO2 nanorod displayed the best electrochemical capacity. All the synthesized MnO2, however, showed a good reversibility and cycling stability, roughly 70% of the initial capacitance retained after 2000 charge/discharge cycles. This work sheds light on a facile approach for synthesis of high-performance metal oxide electrode materials with controllable microstructure.