In situ assembly of MnO2 nanowires/graphene oxide nanosheets composite with high specific capacitance

Graphene oxide (GO) in situ composited with MnO2 nanowires was achieved through a hydrothermal process. The morphology and structure of the products were investigated by using field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectra and X-ray diffraction. The results showed that the product consisted of alpha-MnO2 nanowires with the diameter of 20 similar to 40 nm and the length of 0.5 similar to 2 mu m that well dispersed on the surfaces of GO. The excellent electrochemical performance of as-prepared GO/MnO2 hybrids was obtained due to the unique chemical interactions between GO and MnO2. The maximum specific capacitances of 360.3 F/g measured by chronopotentiometry at a current density of 0.5 A/g were obtained in a 1 M Na2SO4 aqueous solution. This value is much higher than that of pure MnO2 nanowire electrodes (128.0 F/g) and commercial MnO2 microparticles electrodes (22.8 F/g). Furthermore, GO/MnO2 nanowires hybrids also exhibit good cycling stability with more than 93% capacitance retention over 1000 cycles. The present synthesis strategy may be readily extended to the preparation of other hybrids based on GO nanosheets for potential applications in energy storage and conversion devices. (C) 2013 Elsevier Ltd. All rights reserved.