Facile solvothermal synthesis of a graphene nanosheet–bismuth oxide composite and its electrochemical characteristics

This work demonstrates a novel and facile route for preparing graphene-based composites comprising of metal oxide nanoparticles and graphene. A graphene nanosheet–bismuth oxide composite as electrode materials of supercapacitors was firstly synthesized by thermally treating the graphene–bismuth composite, which was obtained through simultaneous solvothermal reduction of the colloidal dispersions of negatively charged graphene oxide sheets in N,N-dimethyl formamide (DMF) solution of bismuth cations at 180 °C. The morphology, composition, and microstructure of the composites together with pure graphite oxide, and graphene were characterized using powder X-ray diffraction (XRD), FT-IR, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetry and differential thermogravimetry (TG–DTG). The electrochemical behaviors were measured by cyclic voltammogram (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The specific capacitance of 255 F g−1 (based on composite) is obtained at a specific current of 1 A g−1 as compared with 71 F g−1 for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757 F g−1 even at 10 A g−1. In addition, the graphene nanosheet–bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility.