Electronic structure and magnetism of various surfaces of the catalytic material Pt3Ni: Density-functional study

A Pt-skin Pt3Ni(111) surface was reported to show high catalytic activity. In this study, we investigated the magnetic properties and electronic structures of the various oriented surfaces of bulk-terminated and Pt-segregated Pt3Ni by using a first-principles calculation method. The magnetic moments of Pt and Ni are appreciably enhanced at the bulk-terminated surfaces compared to the corresponding bulk values, whereas the magnetic moment of Pt on the Pt-segregated Pt3Ni(111) surface is just slightly enhanced because of the reduced number of Ni neighboring atoms. Spin-decomposed density of states shows that the dz2 orbital plays a dominant role in determining the magnetic moments of Pt atoms in the different orientations. The lowering of the d-band center energy (−2.22 to −2.46 to −2.51 to −2.65 eV) in the sequence of bulk-terminated (100), (110), (111), and Pt-segregated (111) surfaces may explain the observed dependence of catalytic activity on surface orientation. Our d-band center calculation suggests that an observed enhanced catalytic activity of a Pt3Ni(111) surface originates from the Pt-segregation.