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ZnO–graphene nanocomposites were synthesized by a one-pot method at room temperature, using graphene oxide as starting material, Zn powder as a precursor of ZnO and as reducing agent in mildly alkaline conditions, followed by post-treatment with potassium hydroxide solution. It is found that the ZnO nanoparticles (average diameter ∼14nm) were dispersed evenly on the graphene sheets. The resulting nanocomposites exhibited excellent capacitative performance (192Fg−1, 20.8kWkg−1) and fluorescent effect. [Copyright &y& Elsevier]

A reduced graphene oxide/multiwalled carbon nanotube (RGO/MWCNT) hybrid sandwiched film with different MWCNTs content was prepared by vacuum-assisted self-assembly from a complex dispersion of graphene oxide (GO) and MWCNTs followed by heat-treating at 200 °C for 1 h in a vacuum oven to reduce the GO into RGO. The free-standing RGO/MWCNT hybrid sandwiched film before heat-treatment showed a layered structure with an entangled network of MWCNTs sandwiched between the GO sheets. This unique structure not merely contribute to remove the oxygen-containing groups in GO during the heat-treatment, but also decrease the defects for electron transfer between RGO layers, which enhances the electrochemical capacitive performances of graphene-based films. A specific capacitance up to 379 F/g was achieved based on RGO/MWCNT with 30 % MWCNTs mass fraction at 0.1 A/g in a 6 M KOH electrolyte. The excellent performance of RGO/MWCNT hybrid sandwiched film signifies the importance of controlling the surface chemistry and sandwiched nanostructure of graphene-based materials. [ABSTRACT FROM AUTHOR]

Abstract: The surface functional groups of thermally reduced graphene nanosheets (TRG) prepared by vacuum promoted thermal expansion of graphene oxide are tailored by progressive carbonization. The residual carbon ratios after annealing at various temperatures from 250 to 1000°C increase progressively from 44.3 to 84.8%. The oxygen containing functional groups are intensively removed at higher annealing temperature. The thermally stable phenols, ethers, and carbonyls become the major components in 1000°C annealed TRG. Though the starting material G250 owns a high specific capacitance of 170.5F/g, the value decreases to only 47.5F/g when the annealing temperature is increased to 1000°C. The oxygen containing functional groups can enhance the capacitance performance of TRGs by introducing abundant pseudocapacitance active sites through reversible Faradic redox reactions. The correlation between the structural evolution and electrochemical performance of TRGs provides new insight for designing graphene based electrodes with controllable properties for advanced supercapacitors. [Copyright &y& Elsevier]