measurementsX-ray diffraction patterns were obtained with a GBC MMA X-raydiffractometer with Cu K radiation. The morphologies and dis-tributions of platinum and PtxCo1−xalloy nanoparticles supportedon carbon were investigated by transmission electron microscopy(TEM) using a JEOL JEM 2011 TEM facility. TEM specimens wereprepared by making a suspension of catalyst powder in ethanol anddepositing a drop of the suspension on a standard carbon-coveredcopper grid.Electrochemical measurements were performed with a CHI660E electrochemical workstation (CH Instrument Company,Shanghai, China). A conventional three-electrode system cell wasemployed. The working electrodes were made by casting carbon-supported nanoparticles (PtxCo1−x/C or Pt/C) as a thin film onto aglass carbon electrode (GCE) with chitosan as a binding agent. Thecounter electrode was Pt foil, and the reference electrode was a sat-urated calomel electrode (SCE). So all potentials are reported withrespect to the SCE throughout this paper