In situ X-ray probing reveals fingerprints of surface platinum oxide.
In situ X-ray absorption spectroscopy (XAS) at the Pt L(3) edge is a useful probe for Pt-O interactions at polymer electrolyte membrane fuel cell (PEMFC) cathodes. We show that XAS using the high energy resolution fluorescence detection (HERFD) mode, applied to a well-defined monolayer Pt/Rh(111) sample where the bulk penetrating hard X-rays probe only surface Pt atoms, provides a unique sensitivity to structure and chemical bonding at the Pt-electrolyte interface. Ab initio multiple-scattering calculations using the FEFF code and complementary extended X-ray absorption fine structure (EXAFS) results indicate that the commonly observed large increase of the white-line at high electrochemical potentials on PEMFC cathodes originates from platinum oxide formation, whereas previously proposed chemisorbed oxygen-containing species merely give rise to subtle spectral changes.
SLAC National Accelerator Laboratory, 2575 Sand Hill Rd, Menlo Park, CA 94025, USA. dfriebel@slac.stanford.edu
Daniel
D
Friebel
Daniel J
DJ
Miller
Christopher P
CP
O'Grady
Toyli
T
Anniyev
John
J
Bargar
Uwe
U
Bergmann
Hirohito
H
Ogasawara
Kjartan Thor
KT
Wikfeldt
Lars G M
LG
Pettersson
Anders
A
Nilsson
D004563:Electrochemistry; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D010984:Platinum / Q000737:chemistry*; D013057:Spectrum Analysis; D013499:Surface Properties; D014965:X-Rays
D010087:Oxides; C514637:platinum oxide; D010984:Platinum; D010100:Oxygen