Hydrothermal preparation of fluorinated graphene hydrogel for high-performance supercapacitors

Fluorinated graphene hydrogels (FGHs) are synthesized through a one-step hydrothermal process and applied as the binder/additive-free electrode materials for supercapacitors. Along with the reduction of graphene oxide (GO), fluorine atoms incorporate into the graphene framework through the substitution process with the residual phenol, ether or carbonyl groups, forming different fluorine species subsequently. The fluorine content and the C-F bond configuration are easily adjusted by the hydrothermal temperature. X-ray photo electron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectra indicate the mainly existent of semi-ionic C-F bonds in the prepared FGHs. The semi-ionic C-F bonds in FGHs facilitate the ion transport, enhance the electrical conductivity and provide active sites for the faradic reaction. Therefore, the electrochemical performances of FGHs are better than the fluorine-free graphene hydrogel prepared by the same hydrothermal process. FGH prepared at the hydrothermal temperature of 150 degrees C exhibit the highest specific capacitance (227 F g(-1)) and the best rate capability. The corresponding symmetric-supercapacitor delivers the power density as high as 50.05 kW Kg(-1) at the current density of 50 A g(-1). These results indicate the FGHs are the ideal electrode materials with the great potential in the field of high-power supercapacitors. (C) 2016 Elsevier B.V. All rights reserved.