Visualization and understanding of the degradation behaviors of a PEFC Pt/C cathode electrocatalyst using a multi-analysis system combining time-resolved quick XAFS, three-dimensional XAFS-CT, and same-view nano-XAFS/STEM-EDS techniques
| Autor: | Tomoya Uruga, Shinobu Takao, Kotaro Higashi, Hirosuke Matsui, Yasuhiro Iwasawa, Mizuki Tada, Gabor Samjeské |
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| Rok vydání: | 2020 |
| Předmět: |
In situ
chemistry.chemical_classification Valence (chemistry) Materials science General Physics and Astronomy 02 engineering and technology Electrolyte Polymer 010402 general chemistry 021001 nanoscience & nanotechnology Electrocatalyst 01 natural sciences Cathode 0104 chemical sciences law.invention X-ray absorption fine structure Chemical engineering chemistry law Nano Physical and Theoretical Chemistry 0210 nano-technology |
| Zdroj: | Physical Chemistry Chemical Physics. 22:18919-18931 |
| ISSN: | 1463-9084 1463-9076 |
| Popis: | We developed a multi-analysis system that can measure in situ time-resolved quick XAFS (QXAFS) and in situ three-dimensional XAFS-CT spatial imaging in the same area of a cathode electrocatalyst layer in a membrane-electrode assembly (MEA) of a polymer electrolyte fuel cell (PEFC) at the BL36XU beamline of SPring-8. The multi-analysis system also achieves ex situ two-dimensional nano-XAFS/STEM-EDS same-view measurements of a sliced MEA fabricated from a given place in the XAFS-CT imaged area at high spatial resolutions under a water–vapor saturated N2 atmosphere using a same-view SiN membrane cell. In this study, we applied the combination method of time-resolved QXAFS/3D XAFS-CT/2D nano-XAFS/STEM-EDS for the first time for the visualization analysis of the anode-gas exchange (AGEX) (simulation of the start-up/shut-down of PEFC vehicles) degradation process of a PEFC MEA Pt/C cathode. The AGEX cycles bring about serious irreversible degradation of both Pt nanoparticles and carbon support due to a spike-like large voltage increase. We could visualize the three-dimensional distribution and two-dimensional depth map of the amount, oxidation state (valence), Pt2+ elution, detachment, and aggregation of Pt species and the formation of carbon voids, where the change and movement of the Pt species in the cathode catalyst layer during the AGEX cycles did not proceed exceeding the 1 μm region. It is very different from the case of an ADT (an accelerated durability test between 0.6–1.0 VRHE)-degraded MEA. We discuss the spatiotemporal behavior of the AGEX degradation process and the degradation mechanism. |
| Databáze: | OpenAIRE |
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