| Abstract Scope |
Recent research on supercapacitors has focused on the development of complex architectures, such as hybrid or asymmetrical electrodes, intended to increase the energy density of the resulting supercapacitors. In this work, functional coatings are grown on a vertically-aligned carbon nanotube forest (VACNT). The morphology and composition of the coatings are studied in detail using SEM, TEM, EDS, and XPS. Pseudo capacitive titania coatings are grown on the VACNTs forming a discontinuous, particle-like morphology. However, the addition of an alumina layer grown on the VACNTs prior to titania growth results in the formation of a continuous, shell-like coating on the VACNTs. The presence of this alumina and titania coating is observed to decrease the series resistance of the supercapacitor, measured with electrochemical impedance spectroscopy, and improve the performance of the device over 1000 cycles when compared to titania-coated VACNT electrodes. In situ TEM experiments provide additional insights into charge storage mechanisms. |