Beneficial Effects of Adsorbate-Induced Surface Segregation of Pt in Nanoporous Metals Fabricated by Dealloying of Ag-Au-Pt Alloys

Abstract

Surface segregation of Pt is investigated in nanoporous metals formed by dealloying of Ag-Au-Pt alloys. By exposing freshly-dealloyed nanostructures to surprisingly low temperatures in the presence of laboratory air, the Pt segregates to the surface of the ligaments thanks to its preferential interaction with oxygen; in contrast, in an inert atmosphere (Ar-H2), Pt mostly remains in the bulk of the ligaments. Moreover, the co-segregation of Pt and O hinders the thermal coarsening of the ligaments. The averaged size of the ligaments, the resulting roughness factor (Rf) and the fraction of Pt atoms on the surface of the ligaments were investigated. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and low energy ion scattering were used to characterize the resulting nanoporous structure, in addition to electrochemical methods such as underpotential deposition of hydrogen and cyclic voltammetry.