The Preparation Of Polyaniline-based Activated Carbons And Study On Their Electrochemical Performance For Supercapacitor

Supercapacitors have gained great attention because of its huge charge/dischargecapability, high power density and high charge/discharge efficiency. It is well knownthat the electrode materials are particularly critical in determining the performance ofsupercapacitors. Carbon materials have been extensively studied for supercapacitorelectrode materials because of their relatively low cost, stable physicochemicalproperties, environmental friendliness. Especially, heteroatoms （such as phosphorus,nitrogen, oxygen, and so on） on the surface of the carbon materials have beeninvestigated greatly for supercapacitor electrode materials. This is due to the fact thatthe heteroatoms can provide the pseudocapacitance for carbon materials throughfaradaic redox reactions. In this article, we have prepared activated carbons frompolyaniline （PANI） via self-assembly method and Potentiostatic method. The carbonnanotubes have been prepared from these polyaniline nanotubes by carbonization andair activation or Chemical activation with K₂CO₃/ZnCl₂. The properties of theobtained materials were characterized by scanning electron microscope （SEM）,transmission electron microscopy （TEM）, Fourier transform infrared spectroscopy（FTIR）, X-ray diffraction （XRD） analysis, elemental analysis, X-ray photoelecgonspectroscopy （XPS）, Brunauer-Emmett-Teller （BET）, galvanostatic charge-discharge,cyclic voltammetry, and electrochemical impedance spectroscopy techniques. Themain contents of the paper are as follows:1. Electrochemical synthesis is characterized on low cost, simple reactioncondition, high purity for the product, and clean production process. In this paper, wesynthesized the bamboo-like structure PANI via potentiostatic method, then preparedactivated carbon materials by carbonization and activation in mixed gas of oxygenand nitrogen. The optimum orthogonal experiment condition of PANI materials: theconcentration of aniline was0.2M, the concentration of H2SO4was0.75M, thereaction voltage was2.2V and the reaction time was4h. The optimum technologicalcondition of activated carbon materials was as follows: the carbonization temperaturewas700℃, the carbonization time was1h, the activation temperature was450℃,the activation time was1.5h. After air activation, the contents of N and O wereincreased, and the BET surface area was increased sharply to928.9m²g^-1.Mesoporous volume and the ratio of mesoporous volume were large. The specific capacitance of the activated carbon obtained was up to285F g^-1, which was obviouslyimproved due to the microporous and mesoporous.2. The activated carbon was prepared from PANI synthesized by self-assemblymethod, K₂CO₃was used as the activation reagent. The optimum technologicalcondition of activated carbon nanotubes via K₂CO₃activation was as follows: theweight ratio of PANI to K₂CO₃was2:1, the heating rate was4℃min^-1, and theactivation temperature was600℃. After K₂CO₃activation, The specific surface areaof the carbon materials was increased sharply to1004.8m²g^-1, and the specificcapacitance of the activated carbon nanotubes was also increased significantly, whosevalue was184F g^-1. The ratio of mesoporous volume in the activated carbon waslarge, which was prepared from PANI through air activation, and the mesoporousstructure made a significant contribution to capacitance of the activated carbonmaterials, so its specific capacitance was higher than the activated carbon nanotubeswith the higher specific surface area, which was prepared from PANI via K₂CO₃activation.3. The activated carbon nanotubes were prepared from PANI synthesized byself-assembly method, ZnCl₂was used as the activation reagent. Orthogonalexperiments were carried out to explore the influence of conditions, and the optimumtechnological condition of activated carbon materials was gained: the weight ratio ofPANI to ZnCl₂was1:1, the heating rate was10℃min^-1, the activation temperaturewas700℃. Under the optimum condition, the specific capacitance of the activatedcarbon nanotubes was up to172F g^-1and the specific surface area was increased to831.3m²g^-1. The specific capacitance under the scan rate of50mV s^-1was still about92%of the specific capacitance under the scan rate of2mV s^-1.