The synthesis of shape-controlled MnO2/graphene composites via a facile one-step hydrothermal method and their application in supercapacitors

Novel MnO2 petal nanosheet and nanorod/graphene composites are successfully fabricated by a facile one-step hydrothermal method through changing the content of the Mn source. The formation mechanism of different morphologies of MnO2/graphene composites have been studied. The structure of the MnO2/graphene is "sandwich"-like, with MnO2 petal nanosheets and nanorods homogeneously anchored on each side of the graphene. Furthermore, the MnO2/graphene composites with different shapes can be used for supercapacitor electrode materials. The experimental results show that the MnO2 petal nanosheet/graphene composite has better capacitance performance than that of the MnO2 nanorod/graphene composite. The MnO2 petal nanosheet/graphene composite shows excellent specific capacitance as high as 516.8 F g−1 at a scan rate of 1 mV s−1 in 1 M Na2SO4 electrolyte and good long-term cycle stability, indicating its potential application to act as a promising electrode material for high-performance supercapacitors. This study provides a facile and in situ method to prepare metal oxide/graphene composite materials and a novel scaffold to construct other metal oxides with graphene for energy storage.