H-2, He and Ar sorption characteristics in a mixture of multiwalled carbon nanotubes (MWCNT), graphite and diamond-like carbon produced as a cathode deposit during the Kratscmer Hoffman arc process were investigated. A dynamic technique was used to determine the adsorption equilibrium parameters in a temperature range of 30-200 degrees C. Adsorption equilibrium constants were evaluated using the moment analysis of the chromatographic peaks. At 30 degrees C, the adsorption equilibrium constant of H-2 on the MWCNT cathode deposit was found to be 8.91 x 10(-4) m(3) kg(-1), whereas it has value of 5.65 x 10(-4) at 200 degrees C. Heats of adsorption of H-2, He and Ar on the MWCNT cathode deposit were determined as -2.89, -2.94 and -3.01 kJ mol(-1), respectively. The values of heat of adsorption obtained indicated weaker interactions of gases, implying physical adsorption of H-2, He and Ar on the MWCNT cathode deposit used. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.