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

详细信息    查看全文

• 作者：Daniel Friebel ; Venkatasubramanian Viswanathan ; Daniel J. Miller ; Toyli Anniyev ; Hirohito Ogasawara ; Ask H. Larsen ; Christopher P. O鈥橤rady ; Jens K. N酶rskov ; Anders Nilsson
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：June 13, 2012
• 年：2012
• 卷：134
• 期：23
• 页码：9664-9671
• 全文大小：553K
• 年卷期：v.134,no.23(June 13, 2012)
• ISSN：1520-5126

文摘

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 L₃ edge reveals characteristic changes of the shape and intensity of the 鈥渨hite-line鈥?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.