PtCo alloy nanoparticles have been deposited on multi-walled carbon nanotubes (MWNTs) without damaging their intrinsic structures by a soft chemical method. X-ray diffraction depicts a good crystallinity of the supported Pt nanoparticles in the composites and reveals the formation of PtCo alloy. Transmission electron microscope (TEM) images show that the PtCo particles are as small as 1-6 nm and uniformly deposited on the MWNT surface. Raman spectroscopy confirms there is a very low defect density on the MWNT surface. Compared with acid-treated MWNT-PtCo, low-defect MWNT-Pt and commercial PtRu catalysts, this low-defect MWNT-PtCo catalyst exhibits excellent electrochemical activity and high poison tolerance toward methanol oxidation reaction. The significantly enhanced performances can be attributed to the good preservation of electronic conductivity of MWNTs, the synergistic effect of the bimetallic active components and high dispersion of PtCo alloy nanoparticles on the MWNT surface. (C) 2012 Elsevier Ltd. All rights reserved.