Fishbone-typed carbon nanofibers (CNFs) that were formed by methane decomposition over silica-supported Ni catalysts were used as catalytic supports for Pt or Pt-Co alloy nanoparticles. The treatment of CNFs with concentrated HNO3 led to the formation of porous structures as well as to the introduction of oxygen-containing functional groups. Pt metal particles of a few nanometers in diameter could be stabilized on the CNFs treated with HNO3 and showed a high tolerance to sintering at high temperatures, whereas Pt metal particles supported on the CNFs without any treatment were seriously aggregated at high temperatures. The porous structures and functional groups in the CNFs worked as anchoring sites for Pt metal nanoparticles. Thus, Pt-Co alloy particles of a few nanometers in diameter could be prepared by using the CNF support since the CNFs inhibited the sintering of the alloy particles during the treatment at high temperatures to allow for alloy formation. (C) 2012 Elsevier B.V. All rights reserved.