Sulfonated Graphene Synthesized via a Green Route and Its Capacitive Properties

An environmentally friendly approach is presented to synthesize sulfonated reduced graphene oxide (S-rGO) by using L- ascorbic acid ( L- AA) and aryl diazonium salt of sulfanilic acid. The preparation conditions have been optimized in order to obtain isolated and conductive S- rGO, and the products have been characterized by Ultraviolet- Visible spectroscopy, Fourier transformed infrared spectroscopy, Raman, X- ray photoelectron spectroscopy and X- ray powder diffraction and electrochemical methods. The results show that the S- rGO sheets possess excellent water- solubility and high electrical conductivity, which implies that the oxygen- containing functional groups have been removed and conjugated sp(2) network has been restored. What's more, the electrochemical measurements reveal that the capacitive performance of the S- rGO has been improved compared with the graphene oxide ( GO) and the reduced graphene oxide ( rGO, reduced by L- AA). The optimum S- rGO exhibits a specific capacitance of 205 F center dot g(-1) and good cycling stability ( 3.9% decreasing after 10000 cycles), which are better than those for graphene oxide ( 109 F center dot g(-1) and decreasing 6.6% after 10000 cycles) and rGO ( 139 F center dot g(-1) and decreasing 11.3% after 10000 cycling). This approach proves a new route to improve the capacitive properties of rGO.