The development of new catalysts system for fuel cell is an important for the clean environment point of view. The rising cost of platinum, the most commonly used metal for catalysis, has also driven research for more efficient catalyst use. Recent findings have supported the suggestions that either alloying or layering Pt with Au can decrease both the rate of catalyst poisoning by species such as the amount of Pt loading necessary in the catalyst. Specifically, “core/shell” catalysts utilize monolayers of Pt for the surface shell and other metallic components or alloys for the core structure. The reduction of the Platinum (Pt) layers deposited on Gold (Au) thin film decrease the rate of catalysts poisoning and the amount of Pt loading necessary in the catalysts. We demonstrate here a careful characterization of the surface alloyed nanostructure for the Pt-Au core-shell system using X-ray Photoelectron Spectroscopy (XPS) methods.