Search

Abstract: Incorporation of reduced graphene oxide (rGO) in Co3O4 matrix is systematically investigated through a chemical route for supercapacitors. The α-Co(OH)2 supported by graphene oxide is first fabricated by a chemical precipitation approach. Thermal decompositions of these precursors at the given temperature (150°C) lead to rGO/Co3O4 composites. Measurement results show that the morphology and electrochemical activity of the rGO/Co3O4 composites are influenced significantly by the mass ratios of rGO to Co3O4. When used as electrode materials in supercapacitors, the composite with mass ratio of 0.22:1 (rGO:Co3O4) achieves the specific capacitance as high as 291Fg−1 at 1Ag−1 in the potential range of −0.4 to 0.55V, as compared with each individual counterpart (56 and 161Fg−1 for rGO and Co3O4, respectively). In addition, the excellent rate capability and well cycling ability are observed in the composite electrodes. The enhanced electrochemical performance is indicative of a positive synergistic effect between rGO and Co3O4. These results suggest the importance and great potential of graphene based composites in the development of high-performance energy-storage systems. [Copyright &y& Elsevier]

Abstract: A hybrid material of graphene oxide (GO) sheets beaded with ZnO nanoparticles was prepared. The material extends over a few hundred square nanometers, in which the ZnO nanoparticles (average diameter (∼5nm)) are dispersed evenly on the GO sheet. Both the surface photovoltage or surface photocurrent intensity for the material are much stronger than for pure ZnO nanoparticles, meaning that the free charge carriers can effectively be transferred from ZnO nanoparticles to GO sheets, which can serve as a probe to monitor the electron transfer from excited ZnO to GO. Anchoring ZnO nanoparticles on two dimensional carbon nanostructures such as GO can pave a way towards the design of ordered nanostructure assemblies that can harvest light energy efficiently. [Copyright &y& Elsevier]

Abstract: 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 255Fg−1 (based on composite) is obtained at a specific current of 1Ag−1 as compared with 71Fg−1 for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757Fg−1 even at 10Ag−1. In addition, the graphene nanosheet–bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility. [Copyright &y& Elsevier]