Cobalt nanoparticles loaded on an activated carbon catalytically excavated the activated carbon when it was heat-treated in a 1 atm stream of a mixture of hydrogen and argon gases at high temperature. The BET Surface area of the activated carbon decreased from 2210 to 1750 m(2) g(-1), and the mesopore volume increased from 0.14 to 0.25 cm(3) g(-1) by heat-treatment at 900 degrees C for 8 h. As for the XRD pattern of the heat-treated specimen. diffraction peaks from the turbostratic carbon phase were observed. This phase was confirmed by TEM both around the cobalt particles and the walls of the pores formed by the excavation.