Balance of Nanostructure and Bimetallic Interactions in Pt Model Fuel Cell Catalysts [electronic resource] : An in Situ XAS and DFT Study

• Ngôn ngữ: eng
• Ký hiệu phân loại: 333.7 Land, recreational and wilderness areas, energy
• Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2012
• Mô tả vật lý: Size: 18 pages : , digital, PDF file.
• Bộ sưu tập: Metadata
• ID: 256770
• Chủ đề: 1. 30 direct energy conversion; 2. 37 inorganic, organic, physical and analytical chemistry; 3. Absorption spectroscopy; 4. Adsorption; 5. Chemisorption; 6. Defects; 7. Density functional method; 8. Detection; 9. Electrocatalysts; 10. Energy resolution; 11. Et al

Tóm tắt

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.