ZnO/reduced graphite oxide composites were synthesized using a two-step method in which KOH reacts with Zn(NO3)2 in the aqueous dispersions of graphite oxide (GO) to form a Zn(OH)2/graphite oxide precursor, followed by thermal treatment in air. It was found that the dispersion of reduced graphene oxide (rGO) sheets within composites was key for achieving an excellent capacitive performance of the samples. However, the mass ratio of ZnO to rGO determined whether rGO sheets within composites were dispersed or agglomerated. The composite achieved homogeneous incorporation of rGO sheets within the ZnO matrix when the mass ratio of ZnO to rGO was equal to 93.3:6.7. This composite, in which the weight percent of rGO was only 6.7%, appeared in the SEM images to be almost entirely filled with rGO sheets coated by ZnO and exhibited high specific capacitance and excellent cycling ability. Furthermore, the sheets overlapped to form a three-dimensional network structure, through which electrolyte ions easily access the surface of the rGO or electrochemical active sites. The homogeneously incorporated rGO sheets were shown to provide 128% enhancement in specific capacitance compared with 135 F g−1 for pure zinc oxide samples. Also, the unexpected phenomena involved in the experimental processes are discussed in detail.

We report a remarkable transformation of multiwalled carbon nanotubes (MWCNTs) to curved graphene nanosheets (CGN) by the Hummers method. Through this simple process, MWCNTs can be cut and unzipped in the transverse and longitudinal directions, respectively. The as-obtained CGN possess the unique hybrid structure of 1D nanotube and 2D graphene. Such a particular structure together with the improved effective surface area affords high specific capacitance and good cycling stability during the charge-discharge process when used as supercapacitor electrodes. The electrochemical measurements show that CGN exhibit higher capacitive properties than pristine MWCNTs in three different types of aqueous electrolytes, 1 M KOH, 1 M H(2)SO(4), and 1 M Na(2)SO(4). A specific capacitance of as high as 256 F g(-1) at a current density of 0.3 A g(-1) is achieved over the CGN material. The improved capacitance may be attributed to high accessibility to electrolyte ions, extended defect density, and increased effective surface area. Meanwhile, this high-yield production of graphene from low cost MWCNTs is important for the scalable synthesis and industrial application of graphene. Furthermore, this novel CGN nanostructure could also be promisingly applied in many fields such as nanoelectronics, sensors, nanocomposites, batteries, and gas storage.

No abstract

Alizarin (AZ) with a multi-electron redox center is selected to functionalize three-dimensional self-assembled graphene hydrogels (SGHs) through non-covalent modification and the electrode material shows a good self-synergy and potential self-matching behavior.

Anthraquinone (AQ) with electrochemically reversible redox couples is selected to functionalize graphene framework (GF) through non-covalent modification and the composite achieves high specific capacitance, good rate capability and long cycle life.