Reduced graphene oxide/carbon nanotube hybrid film as high performance negative electrode for supercapacitor

Interconnecting different carbon building blocks, such as 1-dimensional (1D) carbon nanotubes (CNTs) and 2-dimensional (2D) graphene sheets, is an effective way to build hybrid carbon architectures with fascinating new properties. Here we report the synthesis of a binder-free reduced graphene oxide/carbon nanotube (rGO/CNT) hybrid film and its capacitive behaviour in both positive and negative potential window with 1 M Na2SO4 aqueous electrolyte. It is found that intercalating small amount of CNTs into rGO sheets result in excellent specific capacitance of 272 F g−1 at a scan rate of 5 mV s−1 in negative potential window of −0.8 to 0 V. In contrast, moderate specific capacitance of 132 F g−1 at the same scan rate is obtained in positive potential window of 0 to 0.8 V. The reason of the enhanced capacitance in negative potential window is discussed. We propose that the remarkable improvement of capacitance in negative potential window is mainly due to the strong cation adsorption at the oxidized surface of rGO sheets. The addition of CNTs can significantly improve the rate capability and cyclic stability of the electrode compared to that of pure rGO electrode. As-synthesized rGO/CNT hybrid film shows great potential in neutral aqueous electrolyte based asymmetric supercapacitors as high performance negative electrode, and other applications such as flexible batteries, seawater desalination, and biomedical applications.