Effects of carbon nanotube grafting on the performance of electric double layer capacitors

Carbon nanotubes (CNTs) were grown on polyacrylonitrile (PAN)-based activated carbon cloth (ACC) for use as electrodes in electric double layer capacitors. The catalyst used for the growth of CNTs was sputter-deposited Ni. It was found that the use of sputter-deposited catalyst for the growth CNTs prevents normally observed surface pore blockage on the ACC. The growth of CNTs took place in a thermal chemical vapor deposition chamber. During the CNT growth, ammonia was introduced into the growth chamber for enhancing the CNT growth and limiting the formation of pyrolytic carbon. The resulting CNTs were found to follows the tip growth mode, leading to direct contacts between the CNTs and the ACC fiber surfaces. Because of this and the high electrical conductivity of CNTs, the obtained CNT-grafted ACC electrodes exhibit significantly enhanced electrical conductivity and improved capacitance retention.