Two kinds of MnO2/graphene nanocomposites (M1 and M2) were synthesized by two different reaction procedures. M1 was synthesized as follows: the plate-like MnO2/graphene nanocomposite was obtained by using hydrazine reduction of MnO2/graphene oxide. M2 was formed as follows: the plate-like MnO2 nanospheres was synthesized on the graphene nanosheet which was reduced by hydrazine reduction of graphene oxide. The M1 have a good electrochemical performance and the average capacitance is as high as 250.6 Fg(-1) at 1 A g(-1) in 1 mol L-1 Na2SO4 electrolyte, which is higher than that of the M2 (206.8 F g(-1)). (C) 2014 Elsevier B.V. All rights reserved.