Supercapacitors based on free-standing reduced graphene oxides/carbon nanotubes hybrid films

The freestanding of reduced graphene oxides/carbon nanotubes (rGO/CNTs) hybrid films are synthesized via the simple vacuum filtration and thermal reduction methods. And the electrochemical behaviors of rGO/CNTs hybrid films are investigated in KOH and in Et4NBF4/AN electrolyte, respectively. In three-electrode systems, the rGO/CNTs hybrid films show a maximum specific capacitance of 221 F g−1, a 71% capacitance retention, and an excellent cycle life in 1 M KOH electrolyte. And the electrochemical behaviors of rGO/CNTs films in Et4NBF4/AN electrolyte under three-electrode systems show a maximum specific capacitance of 174 F g−1 and good rate capability. Moreover, a symmetric supercapacitor of rGO/CNTs//rGO/CNTs demonstrates a maximum specific capacitance of 24 F g−1 at 1 A g−1, a energy density of 20.8 Wh kg−1 at 1.27 kW kg−1, and an excellent cycle life of 86.1% retention after 5000 cycles. It suggests that the symmetric supercapacitor could be regarded as an ideal energy storage system.