title: Balance of nanostructure and bimetallic interactions in Pt model fuel cell catalysts: in situ XAS and DFT study.
abstract: We have studied the effect of nanostructuring in Pt monolayer model electrocatalysts on a Rh(111) single-crystal substrate on the adsorption strength of chemisorbed species. In situ high energy resolution fluorescence detection X-ray absorption spectroscopy at the Pt L(3) edge reveals characteristic changes of the shape and intensity of the "white-line" due to chemisorption of atomic hydrogen (H(ad)) at low potentials and oxygen-containing species (O/OH(ad)) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum, we observe a significant destabilization of both H(ad) and O/OH(ad) due to strain and ligand effects induced by the underlying Rh(111) substrate. When Pt is deposited via a wet-chemical route, by contrast, three-dimensional Pt islands are formed. In this case, strain and Rh ligand effects are balanced with higher local thickness of the Pt islands as well as higher defect density, shifting H and OH adsorption energies back toward pure Pt. Using density functional theory, we calculate O adsorption energies and corresponding local ORR activities for fcc 3-fold hollow sites with various local geometries that are present in the three-dimensional Pt islands.
authors.affiliation: Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA. dfriebel@slac.stanford.edu
authors.forename: Daniel
authors.initials: D
authors.lastname: Friebel
authors.forename: Venkatasubramanian
authors.initials: V
authors.lastname: Viswanathan
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Miller
authors.forename: Toyli
authors.initials: T
authors.lastname: Anniyev
authors.forename: Hirohito
authors.initials: H
authors.lastname: Ogasawara
authors.forename: Ask H
authors.initials: AH
authors.lastname: Larsen
authors.forename: Christopher P
authors.initials: CP
authors.lastname: O'Grady
authors.forename: Jens K
authors.initials: JK
authors.lastname: Nørskov
authors.forename: Anders
authors.initials: A
authors.lastname: Nilsson