Web Release Date: October 18,
In Situ Synchrotron X-ray Spectroscopy of Ruthenium Nanoparticles Modified with Selenium for an Oxygen Reduction Reaction
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Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, Clean Energy Research Center, University of Yamanashi, Kofu, Yamanashi, 400-0032 Japan
Received: April 2, 2007
In Final Form: July 9, 2007
Abstract:
We used in situ Se K-edge X-ray spectroscopy to characterize Ru nanoparticles chemically modified with submonolayers of selenium (Se/Ru) [Cao et al. J. Electrochem. Soc. 2006, 153, A869]. X-ray powder diffraction verified that the Se/Ru catalyst had metallic Ru cores. The in situ X-ray absorption near edge structure taken at the open circuit potential showed that there were both elemental and oxidized selenium on the as-prepared Se/Ru samples. All selenium oxide was reduced to the elemental form of selenium by applying negative potentials. By applying positive potentials, selenium was subsequently reoxidized. The analysis of the extended X-ray absorption fine structure shows the appearance of selenium hydration (Se-OH2) in a deaerated solution, which was not observed during the oxygen reduction reaction. We present evidence that Se-free Ru atoms play an important role in the ORR activity of the Se/Ru catalyst studied in this paper.
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