Hydrothermal Self-assembly Synthesis of Mn3O4Reduced Graphene Oxide Hydrogel and Its High Electrochemical Performance for Supercapacitors

In the present work Mn3O4/reduced graphene oxide hydrogel （Mn3O4-rGOH） with three dimensional （3D） networks was fabricated by a hydrothermal self-assembly route. The morphology, composition, and microstructure of the as-obtained samples were characterized using powder X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, thermogravimetry analysis （TG）, atomic absorption spectrometry （AAS）, field emission scanning electron microscopy （FESEM） and transmission electron microscope （TEM）. Moreover, the electrochemical behaviors were evaluated by cyclic voltammogram （CV）, galvanostatic charge-discharge and electrochemical impedance spectroscopy （EIS）. The test results indicated that the hydrogel with 6.9% Mn3O4 achieved specific capacitance of 148 F.g^-1 at a specific current of 1 A.g^-1, and showed excellent cycling stabilily with no decay after 1200 cycles. In addition, its specific capacitance could retain 70% even at 20 A.g^- 1 in comparison with that at 1 A.g ^-1 and the operating window was up to 1.8 V in a neutral electrolyte.

Ruthenium Oxide/Reduced Graphene Oxide Nanoribbon Composite and Its Excellent Rate Capability in Supercapacitor Application

Chemical oxidation is used to cut and unzip multi-walled carbon nanotubes in the transverse direction and the axial direction to form graphene oxide nanoribbon （GONR）. Ruthenium oxide/reduced graphene oxide nanoribbon composite （RuO2/rGONR） with a 72.5 wt% RuO2 loading is synthesized through an aqueous-phase reaction, in which GONR is served as starting material, followed by mild thermal treatment in ambient air. The resulting RuO2/rGONR composite achieves specific capacitance up to 677 F.g l at the current density of 1 A·g^-1 in three-electrode system using 1 mol·L^-1 H2SO4 as electrolyte. The resultant electrode exhibits an excellent rate capability （91.8% retention rate at 20 A·g^-1）. Especially, the symmetric supercapacitor assembled on the basis of RuO2/rGONR electrode delivers high energy density （16.2 Wh·kg^-1） even at the power density of 9885 W·kg^-1, which is very essential for supercapacitors.

Non-Covalent Functionalization of Graphene with Bisphenol A for High-Performance Supercapacitors

The reduced graphene oxide(RGO)/bisphenol A(BPA)composites were prepared by an adsorption-reduction method.The composites are characterized by X-ray diffraction(XRD),UV-vis,thermogravimetric(TG)analysis,field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM).The results confirm that BPA is adsorbed on the basal plane of RGO byπ-πstacking interaction.Furthermore,the electrochemical behaviors were evaluated by cyclic voltammetry,galvanostatic charge/discharge techniques and electrochemical impedance spectroscopy(EIS).The results show that the RGO/BPA nanocomposites exhibit ultrahigh specific capacitance of 466 F•g^(−1) at a current density of 1 A•g^(−1),excellent rate capability(more than 81%retention at 10 A•g^(−1) relative to 1 A•g^(−1))and superior cycling stability(90%capacitance decay after 4000 cycles).Consequently,the RGO/BPA nanocomposites can be regarded as promising electrode materials for supercapacitor applications.