Novel MnO 2 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 MnO 2 /graphene composites have been studied. The structure of the MnO 2 /graphene is "sandwich"-like, with MnO 2 petal nanosheets and nanorods homogeneously anchored on each side of the graphene. Furthermore, the MnO 2 /graphene composites with different shapes can be used for supercapacitor electrode materials. The experimental results show that the MnO 2 petal nanosheet/graphene composite has better capacitance performance than that of the MnO 2 nanorod/graphene composite. The MnO 2 petal nanosheet/graphene composite shows excellent specific capacitance as high as 516.8 F g À1 at a scan rate of 1 mV s À1 in 1 M Na 2 SO 4 electrolyte and good longterm cycle stability, indicating its potential application to act as a promising electrode material for highperformance 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.

Shape controlled functionalized graphene–MnO2 composites with high capacitive performance can be obtained by self-assembly.

The shape-controlled graphene–PANI nanocomposites showing excellent performance as supercapacitor electrode materials were successfully prepared by a facile hydrothermal method without any surfactants.

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