peaks at 40◦and 47◦were indexed to Pt(1 1 1) and (2 0 0), respec-tively. All diffraction lines can be indexed to the face-centered cubic(fcc) phase of platinum (PC-PDF card No. 01-1194). Apart from thetwo strong diffraction peaks of Pt or PtxCo1−xphase, another broaddiffraction peak at about 24◦represents amorphous carbon. Wenoticed that the major diffraction peaks of PtxCo1−xcatalysts aregradually shifted to higher 2 angles with increasing Co content(Table 1). This indicates a contraction of the lattice and confirmsthe formation of Pt–Co alloys due to the incorporation of Co intothe fcc crystal structure of Pt.The morphologies of the as-prepared Pt0.7Co0.3alloy catalystsdeposited on Vulcan XC-72 carbon matrix were observed by FEG-SEM. Fig. 1B shows a SEM image of a typical Pt0.7Co0.3alloy