Highly active 40 wt.% PtRu/C electrocatalysts that can be used as anode in polymer electrolyte membrane fuel cells (PEMFCs) were fabricated by improved impregnation method that introduced formaldehyde as a reducing agent and HCl as a segmentation agent with heat treatments at various temperatures. The morphology of the prepared catalysts was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD), which revealed that the PtRu particles on carbon after heat treatment at 300 degrees C had a very narrow size distribution in the range of 1.5-3.4 nm, and that the average size varied between 2.3 and 2.4 nm. The electrochemical active surface area of the prepared PtRu/C catalysts was determined by CO-stripping voltammetry. In particular, the PtRu nanostructure electrodes heat treated at 300 degrees C showed an excellent catalytic activity because of the metals' large surface area as well as a sufficient degree of alloy formation for CO tolerance. The unit cell performance of the PtRu/C catalyst with heat treatment at 300 degrees C exhibited a power density of 0.67 W cm(-2) which was higher than that of a unit cell with a commercial PtRu/C catalyst (E-TEK) with the same metal loadings. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.