Fundamental electrochemical (EC) properties of carbon nanotubes (CNTs) grown on Ti foil have been systematically investigated. The relationship between EC properties and structural properties is dominated by area of the reacted surface, and there is no significant EC performance on Ti foil. Therefore, the EC reaction is derived from CNTs. The concepts elucidated here regarding EC properties would help greatly in energy-storage applications. (c) 2007 The Electrochemical Society. All rights reserved.