Segregation and Selective Oxidation of Ni Atoms in Pt3Ni(111) in a Low-Pressure Oxygen Environment

Understanding the microscopic mechanism of oxygen interaction with the surfaces of Pt-based alloys is an important issue for applications in various fields such as corrosion and oxygen reaction reduction in fuel cells, for which Pt-based alloys are more efficient catalysts with respect to platinum. Herein, the interaction of oxygen with Pt3Ni(111) has been studied by X-ray photoemission, X-ray absorption, and high-resolution electron energy loss spectroscopies. We have found that the oxidation of Pt3Ni(111) at 600 K leads to the segregation of Ni atoms to the surface region. The presence of Ni atoms at the Pt3Ni(111) surface allows O-2 to dissociate to form NiOx surface species. High-resolution electron energy loss spectroscopy measurements performed on Pt(111), Ni(111), and Pt3Ni(111) directly show that, on the Pt3Ni(111) surface, oxygen binds selectively on Ni sites and, moreover, that the O-Ni bond formed on Pt3Ni is weaker than the O-Pt bond formed on Pt(111).