Balance of Nanostructure and Bimetallic Interactions in Pt Model Fuel Cell Catalysts: In Situ XAS and DFT Study

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...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2012-06, Vol.134 (23), p.9664-9671
Main Authors: Friebel, Daniel, Viswanathan, Venkatasubramanian, Miller, Daniel J, Anniyev, Toyli, Ogasawara, Hirohito, Larsen, Ask H, O’Grady, Christopher P, Nørskov, Jens K, Nilsson, Anders
Format: Article
Language:English
Subjects:
30 DIRECT ENERGY CONVERSION
ABSORPTION SPECTROSCOPY
ADSORPTION
CHEM, MATSCI
CHEMISORPTION
DEFECTS
DENSITY FUNCTIONAL METHOD
DETECTION
ELECTROCATALYSTS
ENERGY RESOLUTION
EVAPORATION
FLUORESCENCE
HYDROGEN
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
MONOCRYSTALS
NANOSTRUCTURES
PLATINUM
RHODIUM 111
SHAPE
STRAINS
SUBSTRATES
THICKNESS
X-RAY SPECTROSCOPY
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Summary: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 (Had) at low potentials and oxygen-containing species (O/OHad) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum, we observe a significant destabilization of both Had and O/OHad 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.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja3003765