Fabrication Of Graphene/Polyaniline Hollow Spheres Nanocomposite And Its Applications For Supercapacitor

In recent years, supercapacitors have attracted more and more interests of researchers due to its high power density, excellent cycling stability, fast charging-discharging rate and operational security compared with other secondary batteries. Among the pseudocapacitive materials, polyaniline(PANI) has been considered as the most promising candidate material due to its extraordinarily fast redox rate, high theoretical pseudocapacitance, low cost and facile synthesis, which attracted extensive attention of researchers. But, PANI inevitably has the defect of poor cycle stability, in order to solve this problem, researchers are committed to preparing for composites that combine PANI with carbon materials or metallic oxides. Owning to its fast charge/discharge rate, high surface area, broad electrochemical window, superior chemical stability, high specific capacitance and environmentally friendly, RGO/PANI composites are standing out in numerous of the nanocomposite. Compared with other structures, the special hollow structure of PANI provides prominent advantages for supercapacitor applications owing to its enhanced specific surface area and reduced transport lengths for both mass and charge transport. However, until now, the studies about hollow structured PANI with RGO composites are still limited. Thus, in this work, we design and prepare a novel sandwich nanostructure of RGO/PANI-HS composites.In this work, we prepared SiO2 microspheres with diameter about 430 nm through St?ber sol-gel procedure, and modified the surface of SiO2 with APTES coupling agent, then used the modified SiO2 as template to synthesize SiO2@PANI microspheres with core-shell structure by in situ polymerization method, finally, removed the SiO2 core to obtain PANI-HS; GO was synthesized by modified Hummers method, and mixed GO solution with SiO2@PANI solution, through the electrostatic adsorption prepared GO/SiO2@PANI composites, and then followed by reduction of GO and removal of SiO2 to obtain RGO/PANI-HS composites. The morphologies, structures and electrochemical performances of materials were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), atomic force microscopy(AFM), Fourier transform infrared spectra(FTIR), X-ray diffraction(XRD), Raman spectra and electrochemical tests. The main research results are as follows:(1)The RGO/PANI-HS composites with a novel sandwich nanostructure have been successfully fabricated via a solution-based co-assembly process, in which the PANI-HS were inserted between the RGO layers.(2) The electrochemical performance of SiO2@PANI reached the best when m(An):m(SiO2) ratio was 2:1. Compared the cases of presence and absence of APTES, when the APTES was present the electrochemical performance of SiO2@PANI was better. Although the specific capacitance and rate performance of PANI-HS were higher than SiO2@PANI, but the cycle stability of PANI-HS was worse than SiO2@PANI.(3)The electrochemical performance of RGO/PANI-HS composites reached the best when m(SiO2@PANI):m(GO) ratio was 2:1. The RGO/PANI-HS composites exhibits a high specific capacitance of 529 F g-1 at the current density of 0.5 A g-1, excellent rate capability(72% even at 10 A g-1) and excellent capacitance retention of 85% after 1000 cycles at a current density of 5 A g-1, which were significantly higher than that of PANI-HS(424 F g-1 at 0.5 A g-1, 62% at 10 A g-1 and 51% after 1000 cycles). These results indicated that the electrochemical performance of RGO/PANI-HS composites has been significantly improved compared with PANI-HS. Therefore, the RGO/PANI-HS composites have a good prospect in the electrode material applications.