In order to investigate the catalytic capacity of metals and metal oxides based on electrospun carbon fibers for improving hydrogen storage, electrospinning and heat treatments were carried out to obtain metal/metal oxide-embedded carbon fibers. Although the fibers were treated with the same activation procedure, they had different pore structures, due to the nature of the metal oxide. When comparing the catalytic capacity of metal and metal oxide, metal exhibits better performance as a catalyst for the improvement of hydrogen storage, when considering the hydrogen storage system. When a metal oxide with an m.p. lower than the temperature of heat treatment was used, the metal oxide was changed to metal during the heat treatment, developing a micropore structure. The activation process produced a high specific surface area of up to 2900 m(2)/g and a pore volume of up to 2.5 cc/g. The amount of hydrogen adsorption reached approximately 3 wt% at 100 bar and room temperature. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved