| Supercapacitors have attracted considerable attention over the past decades due to their unique properties including high power density, excellent cycling performance, wide temperature range, and environmental friendly. The capacitive performance of electrochemical capacitors is influenced by the electrode materials, electrolyte, and the current collector, and the most important factor is the electrode materials. Polyaniline ?PANi? has been widely explored as potential supercapacitor electrode because of its high theoretical capacitance, chemical stability, unusual doping/dedoping properties, and low cost. However, a major problem for PANi is its low rate capability and poor cycling stability arising from continuous volume expansion/shrinkage during repeated charging and discharging process. To resolve this problem, an effective method is to combine the pseudocapacitive PANi with carbon-based materials to form a composite electrode. Graphene nanomesh ?GNM? is composed of graphene sheets which have high-density in-plane nanopores, thus greatly increasing the specific surface area of GNM and offering ion channels fast diffusion of electrolyte across 2D planes. Besides the GNM, another promising substrate for loading pseudoactive PANi is the one-dimensional hollow carbon fibers ?aCF?, which are characterized by good conductivity, plenty of nanopores on the iber walls, high specific surface area, and excellent capacitive performance. In this thesis, we applied the GNM and aCF as conductive scaffolds to grow pseudocapacitive PANi nanocone arrays. The capacitive performance are systematicly investigated by a series of characterization. The mian content of the research is as follows:GNM-PANi composite electrode with different PANi contents were prepared by a low-temperature oxidation polymerization technique. The electrochemical behaviors of the prepared hybrid materials were measured in a two-electrode system. The GNM-PANi with 70 wt% PANi was found to exhibit a specific capacitance of 452 F g-1 at a current density of 1.0 A g-1. It showed a good rate capability. The GNM-PANi-40 and GNM-PANi-55 retained 92% and 98% of their initial capacitances as the current density increased to 50 A g-1. Moreover, the composite electrode also exhibited surprisingly short relaxation time constant of 0.98 s and 0.93 s, and low equivalent series resistance ?ESR? of 3.9 and 3.5 × 103 ohm, respectively, demonstrating the high-rate capability of PANi loading on highly porous GNM.Similarly, we also applied the ID hollow carbon fibers ?aCF? as conductive substrate to grow polyaniline nanocone arrays. The oxygen-enriched functional groups created by HNO3 oxidation on the surface of aCF electrostatically interact with protonated aniline molecules in acid medium. The subsequent chemical oxidative polymerization initiated by ?NH4?2S2O8 yields aCF-PANi composite with PANi nanocone arrays uniformly and strongly coupled on both external and internal surface of aCF. The prepared hollow carbon fibers/polyaniline with 31 wt% PANi ?aCF-PANi-31? composite exhibited a specific capacitance of 364 F g-1, while retaining 70% of initial capacitance as current density increased up to 20 A g-1.More interestingly, it delivered an excellent cycling stability with 92.5% capacitance retention and 98.6% Coulombic efficiency even after 5000 continuous cycles, suggesting that the strong interaction between PANi and aCF is crucial for achieving high specific capacitance and high rate capability simultaneously. |
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