Hierarchical architecture of ultrashort carbon nanotubes/polyaniline nanocables coated on graphene sheets for advanced supercapacitors

Multilayer super-short carbon nanotubes (SSCNTs) could be prepared by tailoring raw multiwalled carbon nanotubes (MWCNTs) with mechanical-stirring and ultrasonic oxidation-cut method. The SSCNTs/polyaniline/reduced graphene oxide (SSCNTs/PANI/RGO) ternary hybrid composite was fabricated by reducing SSCNTs/PANI/GO precursor prepared by self-assembly from the complex dispersion of graphene oxide (GO) and the as-prepared SSCNTs/PANI nanocables, followed by redoping and reoxidation of the reduced PANI to restore the conducting structure of PANI in the ternary composite. The microscope images indicated that SSCNTs/PANI nanocables could uniformly distribute in the conductive network of graphene sheets and prevent the agglomeration of graphene. Such the hierarchical structure perfectly facilitates the contact between PANI for faradaic energy storage and electrolyte ions, and efficiently utilizes the double-layer capacitance of SSCNTs and graphene sheets at the electrode–electrolyte interfaces. The maximum specific capacitance of the SSCNTs/PANI/RGO composite achieved 845 F g⁻¹, which was much higher than that of pure PANI and SSCNTs/PANI nanocables. Moreover, the ternary composite also showed the good cycling stability, retaining about 96% of its initial capacitance after 1000 cycles because of the synergistic effect and conductive network of SSCNTs/PANI nanocables and graphene sheets. Therefore, the combined effects between SSCNTs/PANI nanocables and graphene sheets taking advantage of both charging and faradaic processes could readily explain the excellent electrochemical performance for supercapacitors.