Preparation And Supercapacitive Performance Of Three-Dimensional Graphene/Polyaniline Composite

In this thesis, graphite oxide was prepared by improved Hummers method, and graphene oxide(GOS) was prepared from graphite oxide by liquid-phase exfoliation added with ultrasonic; three-dimensional graphene(3DGS) was prepared from GOS, which was treated as the precursor, in different hydrothermal temperature. And then by using the opposite charge on the surface of GOS and polyaniline(PANI), One-step and two-steps methods were performed to prepared there-dimensional graphene/PANI composite materials(3DGP-A/B). XRD, FT-IR, Raman, XPS, AFM, SEM, TEM and electrochemical workstation were used to study the morphology, structure and supercapacitive performance of 3DGS and 3DGP-A/B, and the formation mechanism of 3DGS and 3DGP-A/B was further uncovered.The results show that the thickness and size of graphite oxide decrease continually with the increasing of ultrasonic time, and the inner morphology of 3DGS transform from flaky to porous and reticulated structure; the reduction degree of GOS increase while the there-dimensional structural size of 3DGS decrease gradually with the increasing of the hydrothermal temperature. When the ultrasonic time is 120 min and the hydrothermal temperature is 180 °C, the prepared 3DGS possesses the most evenly porous and reticulated structure, and also the best supercapacitive performance, the best specific capacity is 314 F·g-1 and the retention rate of the capacity is 87% after 5000 charge-discharge cycles.During the one-step hydrothermal method processes to prepare 3DGP-A, the hybrid of GOS and PANI was put into the hydrothermal condition, GOS transform to 3DGS by self-assembly, and PANI was inlaid into the there-dimensional structure. In this way, the structural stability of PANI and the excellent network of 3DGS are maintained, which can provide good transm ission path for ions and big surface for storage of charges when this material is used as electrode material. However, the agglomerates of PANI occur when the content of PANI is excessive. By contrast, when the mass ratio of GOS to PANI is 1:1, the 3DGP-A possesses the best supercapacitive performance; the specific capacity is 758 F·g-1 at the current density of 0.5 A·g-1, and the retention rate of the capacity is 86% after 1000 charge-discharge cycles, which suggest good rate capability and cycle stability. The supercapacitive performance of 3DGP-A is far better than that of 3DGS and PANI.During the two-steps hydrothermal method processes to prepare 3DGP-B, the in situ polymerization of the first step can make PANI disperse evenly on the surface of GOS; then the mixture of the obtained GOS/PANI and GOS was performed the hydrothermal process. Compared with, one-step method, the PANI disperse more evenly in the graphene interlayer spacing in 3DGP-B. In this way, not only the agglomerates of graphene are remit ted efficiently, and the specific surface is larger, but also the excellent network of 3DGS is maintained. When the mass ratio of GOS to GOS/PANI is 1:2, the 3DGP-B possesses the best supercapacitive performance; the specific capacity is 712 F·g-1 at the current density of 0.5 A·g-1, and the retention rate of the capacity is 88% after 1000 charge-discharge cycles, the energy density is 75 Wh·Kg-1, which suggest better supercapacitive performance than that of 3DGP-A prepared by one-step method.