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Updated: Feb 13, 2026
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Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells
Published on: September 20, 2012
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Ambient Pressure Hard X-ray Photoelectron Spectroscopy for Functional Material Systems as Fuel Cells under Working
Yasumasa Takagi1, Tomoya Uruga2,3, Mizuki Tada4
1Department of Materials Molecular Science , Institute for Molecular Science , Myodaiji-cho, Okazaki , Aichi 444-8585 , Japan.
Accounts of Chemical Research
|March 7, 2018
Summary
We developed a new X-ray photoelectron spectroscopy technique for analyzing materials under ambient conditions. This method reveals that platinum nanoparticles in fuel cells only oxidize to divalent states, even under operating voltage.
Area of Science:
- Surface Science and Catalysis
- Materials Science and Engineering
- Electrochemistry and Energy Storage
Background:
- Heterogeneous interfaces are critical for functional materials in catalysis, batteries, and devices.
- Understanding interface behavior under realistic conditions is essential for advanced material design.
- X-ray photoelectron spectroscopy (XPS) is a key technique, but typically requires high vacuum.
Purpose of the Study:
- To review a novel technique for hard X-ray photoelectron spectroscopy (HAXPES) under real ambient pressure (10^5 Pa).
- To investigate the electronic states of platinum nanoparticles in polymer electrolyte fuel cells (PEFCs) under operating voltage.
- To demonstrate the utility of ambient pressure HAXPES for in situ analysis of functional materials.
Main Methods:
- Development and application of a windowless electron spectrometer system for ambient pressure HAXPES.
- Utilized synchrotron radiation hard X-rays (8 keV) for measurements.
- Investigated hydrogen storage in Pd nanoparticles and electronic states of Pt/C catalysts in PEFCs under voltage.
Main Results:
- Ambient pressure HAXPES successfully measured spectra under real atmospheric conditions.
- Pd nanoparticles showed abrupt spectral changes with hydrogen pressure, indicating phase transformation-like behavior.
- Pt nanoparticles in PEFCs showed oxidation only to divalent states (Pt(II)), with no detectable tetravalent Pt (Pt(IV)) even at ~1.4 V.
- Pt oxidation was limited to the surface layer of nanoparticles, with no participation from inner atoms.
- Spectra exhibited voltage-dependent hysteresis during voltage cycling.
Conclusions:
- Ambient pressure HAXPES is a powerful in situ tool for studying material interfaces under realistic conditions.
- Pt oxidation in PEFC cathodes is surface-limited and does not form Pt(IV) species under operating voltages.
- The technique provides fundamental insights into the electronic structure and reaction mechanisms of functional materials.
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