Abstract Details
| Electronic Structure Effect in Improved Catalytic Activity of Strained Alloy Nanoparticles | |
|---|---|
| Abstract ID | MAT-26 |
| Presenter | Toyli Anniyev |
| Presentation Type | Poster |
| Full Author List | T. Anniyev (1) , S. Koh (2) , L. Näslund (1) , H. Ogasawara (1) , P. Strasser (2) , M. Toney (1) , A. Nilsson (1) |
| Affiliations | (1) Stanford Synchrotron Radiation Laboratory (2) Dept. of Chemical and Biomolecular Engineering, University of Houston |
| Category | Materials Science |
| Abstract | A new family of Pt-Cu nanoparticle alloy electrocatalysts were identified as having the highest ever reported ORR activities of up to 5-6x compared to pure Pt electrocatalysts. The composition of the surface, lattice arrangement and electronic structure of these catalysts have been characterized by synchrotron based x-ray diffraction and photoelectron spectroscopy methods. The results obtained show that there is a Cu-Pt alloy shell in these nanopaticles, indicating the formation of a core-shell structure upon dealloying. |
| Footnotes | |
| Funding Acknowledgement | This work was supported by the Division of Material Sciences and Engineering, Office of Basic Energy Sciences, Department of Energy under the auspices of the President's Hydrogen Fuel Initiative, and through the Stanford Synchrotron Radiation Laboratory. SEM images were obtained at Molecular Foundry, LBNL. We also want to thank Karren More and Larry Allard from Oak Ridge National Lab, SHaRE User Facility for helping to take the TEM image |
| In Situ XAS and XRD Studies of M(111)/Pt/Electrolyte Interfaces | |
|---|---|
| Abstract ID | MAT-27 |
| Presenter | Toyli Anniyev |
| Presentation Type | Poster |
| Full Author List | Daniel Friebel (1) , Toyli Anniyev (1) , Hirohito Ogasawara (1) , Johan Stålgren (1) , Michael F. Toney (1) , John Bargar (1) , Uwe Bergmann (1) , Anders Nilsson (1) |
| Affiliations | (1) SSRL |
| Category | Materials Science |
| Abstract | Within the scope of our current research project on fuel cell catalysis, we use crystal truncation rod scattering and Pt L-edge x-ray absorption spectroscopy to study the geometric and electronic structure of well defined Pt-modified M(111) surfaces (M = Cu, Au, Rh, Pt, Cu3Pt) in situ, i.e. while in contact with electrolyte and under potential control. The use of Pt monolayers on foreign metal substrates dramatically enhances the surface sensitivity of the hard x-ray probe and, furthermore, elucidates the influence of metal-metal interactions and interfacial strain on the catalytic activity.
Two complementary designs for electrochemical cells can be used, where the electrolyte either forms a very thin layer, allowing for measurements in a broad x-ray energy range, or a several mm thick droplet. The latter design is suitable only for higher x-ray energies, but can be used also under very high electrochemical currents. We present our preliminary results from Pt L3-edge grazing incidence x-ray absorption fine structure measurements of 1 ML Pt on Au(111) in 0.01 M NaOH solution. The spectra show remarkable changes both in the white line intensity as well as the EXAFS with increasing electrode potentials. These can be attributed to the transition from an adsorbate (H2O or OH) covered metallic Pt layer at lower potentials to a Pt-oxide at higher potentials. |
| Footnotes | |
| Funding Acknowledgement | This work was supported by the Office of Basic Energy Sciences, US Department of Energy, under the auspices of the President's Hydrogen Fuel Initiative and through the Stanford Synchrotron Radiation Laboratory. D.F. is grateful to the Alexander von Humboldt Foundation for a Feodor Lynen fellowship. |