Pore structures of multi-walled carbon nanotubes activated by air, CO2 and KOH

Multi-walled carbon nanotubes (MWNTs) synthesized by the catalytic decomposition of benzene were activated by KOH, CO2 or air. The adsorption isotherms of the activated MWNTs were analyzed and their pore size distributions were obtained. The results showed that the specific surface areas of the MWNTs activated by KOH, CO2 and air were increased to 785 m(2)/g, 429 m(2)/g and 270 m(2)/g, respectively. The MWNTs activated by KOH were rich in micropores and mesopores, especially high mesopores having volumes up to 1.04 cm(3)/g. The CO2-activated MWNTs also had many micropores while the air-activated MWNTs had a much smaller micropore volume. The morphologies of the activated MWNTs were examined by transmission electron microscopy and high resolution transmission electron microscopy, and the activation mechanisms were discussed.