The influence of pretreatment on multi-wall carbon nanotubes for electrochemical capacitors

Multi-wall carbon nanotubes (MWCNTs) prepared by chemical vapor deposition, were pretreated by ball milling, chemical activation and ammoxidation and the influence of the pretreatment on their electrochemical capacitance was investigated. Results show that MWCNTs can be shortened and broken by ball milling and chemical activation, and as a result their surface area and pore volume are increased. However, ammoxidation decreases the surface area of the activated MWCNTs. The electrical conductivity of the ball-milled MWCNTs is the smallest while that of the ammoxidated is the largest. The specific capacitances of the ball-milled and the activated MWCNTs are close, but higher than that of the ammoxidated MWCNTs. The capacitances of the MWCNTs pretreated by ball milling, chemical activation and ammoxidation are reduced by 17%, 27% and 13%, respectively, when the discharge current density is increased from 5 to 100 mA/g.