Enhanced electrochemical capacitive performance of “sandwich-like” MWCNTs/PANI/PSS-GR electrode materials

A novel "sandwich-like" MWCNTs/PANI/PSS-GR nanocomposites are achieved via in situ chemical oxidative polymerization and electrostatic adsorption between the negatively-charged poly(sodium 4-styrenesulfonate) (PSS) modified graphene (GR) nanosheets and the positively-charged polyaniline (PANI) on the surface of multiwalled carbon nanotubes (MWCNTs). The morphology and structure of the composites are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible (UV-vis) and Fourier transform infrared (FT-IR), respectively. It is clearly seen that the PANI is uniformly coated on the surface of MWCNTs to form the MWCNTs/PANI bundles with diameter around 60 nm, and then the obtained MWCNTs/PANI are successfully coated on the surface of the PSS-GR nanosheets. In addition, the results of UV-vis and FTIR confirm the successful synthesis of MWCNTs/PANI/PSS-GR nanocomposites and the existence of interaction between PSS-GR and MWCNTs/PANI. The results of electrochemical tests demonstrate that the "sandwich-like" nanocomposites present superior electrochemical properties in comparison with pure PANI and MWCNTs/PANI, which can ascribe to the structure advantage and the synergistic effect of MWCNTs, PANI and GR nanosheets. The specific capacitance (SC) of MWCNTs/PANI/PSS-GR nanocomposites is 602.5 F g(-1) at the current density of 0.5 A g (-1) in a three-electrode system, and still keeps 332.5 F g (-1) (0.5 A g (-1)) in a symmetric two-electrode system. Furthermore, 78.32% of the initial specific capacitance is retained after 2000 charging/discharging cycles, which is much better than that of pure PANI.