Abstract
In this research, it is to illustrate MnO2 electrodeposit onto arrayed carbon nanotubes (CNTs) with fence type and normal type nanocomposite electrodes, then observing and comparing the differences of the composition structure, morphology and electrochemical properties. Since the surface of arrayed CNTs is high density, and not easy to uniformly deposit MnO2, so using the method of fence type can promote the proliferation of electroplating solution to diffuse into the dense arrayed CNTs during electrodepositing process. First, the arrayed CNTs are grown on Ti metal plate by microwave plasma-enhanced chemical vapor deposition(MPECVD), follow by a hydrophilic treatment in HNO3 solution. The electrode is then placed in KMnO4 solution to deposit MnO2 on CNTs by cyclic voltammetry; the potential range is applied between -1~1 V, and using different concentration in KMnO4 solution to achieve the optimum of the specific capacitance. The composition structure and morphology of nanocomposite electrodes are characterized by using Raman spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The electrochemical performance is analyzed for the specific capacitance, long time stability and electrochemical impedance spectroscopy, using cyclic voltammetry in the electrolyte of 0.5 M Na2SO4 and potential range and scan rate between 0~0.9 V and 10~1000 mV/s, respectively. The electrochemical measures the optimum deposit conditions of both the normal and fence type nanocomposite electrodes. At 10 mV/s, the specific capacitance value is 150.6 F/g versus 175.7 F/g, and 90.1 F/g versus 89.2 F/g at 1000 mV/s, respectively. Besides, after 1000 cycles at 50 mV/s the capacitance retention can achieve 94 % versus 99 %. Thus, this experiment reveals that the fence type of MnO2/CNT nanocomposite electrodes had better performance, which can be deemed a potential method for the development of electrode materials for supercapacitors.