| AVS 56th International Symposium & Exhibition | |
| In Situ Microscopy and Spectroscopy: Interfacial and Nanoscale Science Topical Conference | Thursday Sessions |
| Session IS+AS-ThA |
| Session: | In-Situ Microscopy and Spectroscopy: Surface Reactions |
| Presenter: | D. Friebel, Stanford Synchrotron Radiation Lightsource |
| Authors: | D. Friebel, Stanford Synchrotron Radiation Lightsource D.J. Miller, Stanford Synchrotron Radiation Lightsource H. Ogasawara, Stanford Synchrotron Radiation Lightsource T. Anniyev, Stanford Synchrotron Radiation Lightsource C.P. O'Grady, Stanford Synchrotron Radiation Lightsource U. Bergmann, Stanford Synchrotron Radiation Lightsource J. Bargar, Stanford Synchrotron Radiation Lightsource A. Nilsson, Stanford Synchrotron Radiation Lightsource K.T. Wikfeldt, Stockholm University, Sweden L.G.M. Pettersson, Stockholm University, Sweden |
| Correspondent: | Click to Email |
The oxygen reduction reaction at Pt electrodes has a high overpotential which drastically reduces the efficiency of fuel cells. The origin of the overpotential has been seen in the formation of stable Pt-O species at high potentials. Aiming at an unambiguous characterization of such Pt-O species, we use in situ grazing incidence x-ray absorption spectroscopy at the Pt L3 edge to study the geometric and electronic structure of ultrathin Pt layers on Rh(111) and Rh(221) substrates as a function of the electrochemical potential. The use of Pt monolayers on a foreign metal substrate makes the bulk-penetrating hard x-ray probe surface sensitive and, furthermore, can be used for a variety of substrates to elucidate the influence of metal-metal interactions and interfacial strain on the catalytic activity of the Pt layer. The stepped Rh(221) surface serves as a well defined model substrate to study the influence of defects which are also expected to occur in nanoparticle catalysts.
We present our results from Pt L3-edge grazing incidence x-ray absorption fine structure (GIXAFS) and high energy resolution fluorescence detection (HERFD) XAS measurements of an ultrathin Pt layer on Rh(111) in 0.01 M HClO4 solution. The Pt layer was produced by UHV evaporation. In the HERFD-XAS experiment, we used a multi-crystal analyzer to reduce the core hole lifetime broadening. The high resolution spectra reveal additional spectral features of the near-edge region which can be theoretically modeled using the FEFF8 code and thus allow us to build an accurate structure model of the Pt/electrolyte interface.