The Performance Of Carbon Nanotubes, Polyaniline And Their Composite Materials In Different Electrolytes

Supercapacitor is a new type of energy storage component, which functionsbetween electrostatic capacitor and battery. Supercapacitor has high capacitor, and itsenergy density is higher than electrostatic capacitor, while it has a greater powerdensity than batteries. Thus, supercapacitor has a broad and important application inmany scientiifc ifelds. Herein，we use the carbon nanotube CNT)，polyaniline （PANI）and polyaniline/carbon nanotube composites （PANI/CNT） as the supercapacitorelectrode materials. The performance of the prepared materials were characterized bya trail of modern physical methods, such as power X-ray diffraction （XRD），scanningelectron microscope （SEM） and N2adsorption and desorption measurements. In orderto study the influences of the preparation of PANI and PANI/CNT and treatmentconditions on capacitance characteristics, the electrochemical properties wereevaluated by cyclic voltammetry （CV）, galvanostatic charge/discharge （CP）, andelectrochemical impedance spectroscopy （EIS） measurements, et al. We also talkedabout the electrochemical behavior of redox-active electrolytes. The conclusions fromexperiments are shown as follows:Firstly. The electrochemical performances of activated carbon nanotubes whichis activated by air treatment, as electrode material is studied in ifve kinds ofelectrolyte, which are sulfuric acid, hydroquinone/sulfuric acid, potassium hydroxide，sodium sulfate and tetrabutylammonium tetrafluoroborate/acetonitrile. The studyshowed that the speciifc capacitance of carbon nanotubes in the sulfuric acid andhydroquinone/sulfuric acid is187F g₁and380F g₁，respectively. This is due to theoxidation reaction of hydroquinone pseudocapacitance, substantially increased thespeciifc capacitance of the capacitor. The speciifc capacitance of the electrode inpotassium hydroxide is198F g₁. In addition, the speciifc capacitance in sodiumsulfate and tetrabutylammonium tetralfuoroborate/acetonitrile is relatively poor.Secondly. Polyaniline with spherical nanostructures were prepared by usingspherical M11O2as reactive templates in acidic medium. Orthogonal experiments werecarried out to investigate the inlfuence of conditions to the electrochemical propertiesof the polyaniline. The optimum technological condition for polyaniline were shownas follows: the activation temperature was0°C，the molar ratio of M11O2to Anw_asl:l，the deepness of H+was0.2mol L1，and the reaction time was10h. Theelectrochemical properties of polyaniline in sulfuric acid and hydroquinone/sulfiiric acid have been studied, the specific capacitance reached as high as483and573F_g1，respectively. After2000cycles of charge and discharge, the speciifc capacitanceremained38.4%and38.2%of the initial capacity, respectively.Lastly. PANI/CNT composite material was prepared by chemical oxidativepolymerization. The experimental results via orthogonal experiments testiifed that theweight ratio of PANI to CNT was the major factor which inlfuenced the capacitanceof the samples. The optimum technological condition for PANI/CNT compositematerials: the weight ratio of PANI to CNT was8:1，the deepness of H+was1.5molL₁, the deepness of An was0.2mol L₁and the reaction time was10h. The largestspeciifc capacitance was397F_g1. The results show that the speciifc capacitance ofthe composite material is higher than the carbon nanotubers, and the cycle stability isbetter than polyaniline. The speciifc capacitance of the composite material is as highas549F "g1in hydroquinone/sulfuric acid solution.