Large scale synthesized sulphonated reduced graphene oxide: A high performance material for electrochemical capacitors

Large scale reduced graphene oxide (RGO) with sulfonic acid groups (SRGO) has been synthesized by a one-step facial method for high performance electrochemical capacitors (ECs). The as-prepared SRGO shows an enhanced specific surface from 254 to 434 m² g^-1 and bulk conductivity from 2 × 10^-4 to 2.5 × 10^-4 S m compared with that of pristine RGO. An asymmetric EC was assembled with SRGO as the working electrode and Pt as the counter electrode immersed in a 1 M neutral aqueous Na₂SO₄ solution. The results showed that a maximum specific capacitance of 130 F g^-1 was achieved by the SRGO, which is much higher than that of pristine RGO. The SRGO also exhibits a high rate capability and superior cycling stability of more than 99% retention of the specific capacitance after 1000 cycles. Furthermore, it also exhibits excellent specific energy and power densities of 14.6 W h kg^-1 and 50 W kg ^-1 at a current density of 100 mA g^-1, respectively. These results suggest that our SRGO material could be a very promising and versatile building block for carbon-based materials as electrodes towards the next generation of high-performance ECs.