A facile one-step hydrothermal method to produce α-MnO2/graphene sheet composites and its electrochemical properties

A composite of graphene sheet (GNS) supported by nanotube-like MnO2 nanocrystalline (α-MnO2/GNS composites) has been fabricated through a facile one-step hydrothermal method. The nanosized MnO2 particles were homogeneously distributed on GNS, which have been confirmed by transmission electron microscopy analysis (TEM). The structure, composition and electrochemical properties of α-MnO2/GNS composites were investigated by means of selective-area electron diffraction (SAED), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), cyclic voltammetry (CV) curves and Galvanostatic charge–discharge curves. α-MnO2/GNS composites exhibited a high specific capacitance of 116F·g−1 in 1M Na2SO4 electrolyte. In addition, the α-MnO2/GNS composite electrode shows good long-term cycle stability (only 11.99% decrease of the specific capacitance is observed after 1000 charge–discharge cycles). This paper reported a rapid and facile method to prepare α-MnO2/GNS composites as novel electrode materials by hydrothermal method. The schematic illustration of the structure of this hybrid material is shown in Fig. 1. GO contains a large number of CO, COH and COOH. In the process of hydrothermal reaction, CO converts to CO2, at the same time, GO loses functional groups and generates GNS in situ. For this composite, GNS serves mainly as a highly conductive support, which can also provide a large surface for the deposition of nanoscale MnO2 nanotubes with an outer diameter of about 20–25nm. The excellent interfacial contact and increased contact area between MnO2 and GNS can significantly promote the electrical conductivity of the electrode due to the high electrical conductivity of graphene. The composites exhibit an overall specific capacitance of 116F·g−1 and good long-term cycle stability. [Display omitted] ► α-MnO2/graphene nanosheets composites were produced by one step way via graphene oxide and KMnO4 as raw materials. ► Reaction process is very simple and it is obtained by 200°C hydrothermal reaction for 3h. ► The composites exhibit overall specific capacitance of 116F·g−1 and good long-term cycle stability.