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D. Neagu (a), L. Bekris (a), E.I. Papaioannou (a) and I.S. Metcalfe (a), Angew. Chem. Int. Ed. 59, 2510-2519 (2020); https://doi.org/10.1002/
anie.201915140. (a) School of Engineering, Newcastle University (UK)
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ATOMIC-SCALE MECHANISMS OF PLATINUM CATALYST DEGRADATION
The lifetime of platinum catalysts in electrochemical energy-conversion devices such as fuel cells is severely shortened by electrochemical oxidation and reduction processes. In-situ studies with high-energy surface X-ray diffraction (SXRD) now provide a detailed atomistic picture showing how the metal atoms are extracted from the surface during these processes.
PRINCIPAL PUBLICATION AND AUTHORS
Additionally, the ability to disperse metal nanoparticles within oxides could enable new
opportunities in the design of magnetic or thermoelectric materials.
For current low-temperature hydrogen-oxygen fuel cells used in the upcoming generation of commercial fuel cell vehicles, platinum is still the catalyst of choice, especially for the cathode side. However, catalyst lifetime and performance remain a problem for large-scale commercialisation. It has been known for some time that electrochemical oxidation and subsequent oxide reduction lead to irreversible structural changes, as well as platinum dissolution, but the fundamental understanding
of these complex processes is still rudimentary. A detailed atomistic picture of the steps by which these ultrathin oxide layers form existed up to now only for the close-packed Pt(111) surface . Previous in-situ studies of that surface used surface X-ray diffraction (SXRD) techniques to establish the precise locations of the first Pt atoms that move out of their lattice sites in a place-exchange process , and found good agreement with density functional theory (DFT) calculations . Provided the
Fig. 120: a) Correlation between Pt(hkl) dissolution and restructuring behaviour in 0.1 M HClO4. b) Example of Pt(100) crystal truncation rod changes with increasing oxidation, measured by in-situ high-energy surface X-ray diffraction. c) Pt extraction
mechanisms, obtained from DFT calculations (adapted from T. Fuchs et al., Nat. Catal. 3, 754 (2020)).