SSRL Scientists Confirm Method to Make Platinum a Better CatalystSSRL Science Summary - July 2012
The ability to customize and control the activities of scarce, expensive transition metal catalysts is extremely important for the development of economical industrial and energy-saving processes. Over the years several methods have been suggested, especially for processes employing platinum, the most active metal catalyst in many important reactions.
One promising option is to tune chemical functionality by implementing a ligand effect – in other words, by changing the atomic nearest neighbor environment, a conceptually simple way to modify the electronic structure of platinum to enhance its catalytic activity. However, confirming the effect experimentally has been difficult; conventional methods have been unable to disentangle the various constituents of such a catalyst's electronic structure.
Now scientists at the Stanford Synchrotron Radiation Lightsource have used the unique capabilities of SSRL Beam Line 13-2 to study the ligand effect in platinum. They used oxygen-resonant X-ray emission and absorption spectroscopies to look at Pt(111) with either nickel or cobalt embedded in the subsurface region. These spectroscopic techniques provided the means to probe the density of states (DOS) projected on an atomic site in both occupied and unoccupied electronic states. Because of element specificity, the DOS of chemisorbed oxygen atoms could be disentangled from the substrate states and any change in the platinum-oxygen chemical bond probed directly.
The researchers used these element-specific core level spectroscopy techniques to separately probe the catalyst's metal valence states and the density of the adsorbate (oxygen) states, and were able to show changes in the strength of the bonding between platinum and its oxygen and hydrogen adsorbates.. This demonstrated how to modify the electronic configuration of the adsorbate-metal bond and how the resulting effect can translate to improved catalytic activity.
This work is supported by the Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under contract DE-AC02-76SF00515. This research was carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences.
Primary Citation
- T. Anniyev, S. Kaya, S. Rajasekaran, H. Ogasawara, D. Nordlund and A. Nilsson, "Tuning the Metal-Adsorbate Chemical Bond through the Ligand Effect on Platinum Subsurface Alloys", Angew. Chem., Int. Ed. Engl. 51, 7724 (2012) doi: 10.1002/anie.201201068
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Contacts
Sarp Kaya, SUNCAT
Hirohito Ogasawara, SSRL
Anders Nilsson, SUNCAT
