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Towards time resolution in EXAFS of fuel cell electrocatalysts

Towards time resolution in EXAFS of fuel cell electrocatalysts
Towards time resolution in EXAFS of fuel cell electrocatalysts

Mechanistic and kinetic investigations of fuel cell reactions in real time has not been possible with the conventional XAS technique due to the protracted data collection time. Synchrotron instrumentation improvements have reduced the data collection time to minutes with QuEXAFS and installation of a bent crystal monochromator allows the entire data range to be collected simultaneously with EDE.

In situ X-ray absorption spectra of Pt/C electrodes were collected by conventional XAS, QuEXAFS, and EDE techniques, and are compared; data collection times were 40 mins, 60 s, and 1.9 s respectively. Conventional and QuEXAFS spectra were of similar data quality whereas EDE data exhibited a significant increase in the noise and a decrease in resolution. A shortened data range from k = 17 Å-1 for conventional data to 13 Å-1 for QuEXAFS, and 9 Å-1 for EDE causes an artificial decrease in the calculated coordination numbers. It was concluded that QuEXAFS and EDE would not lead to accurate calculated structural parameters.

Further modifications to the beamline improved the signal to noise ratio and resolution of QuEXAFS and EDE spectra. QuEXAFS therefore replaced conventional XAS since the data was comparable in quality and took a third of the time to collect. The data range of EDE spectra was extended to k = 14 Å-1 and a new PC system allowed for faster and structural parameters. Subsequently, it was concluded that future developments are required on the beamline to increase the signal to noise ratio of the data collected and increase the energy range available. The signal to noise ratio may be improved with a higher energy beam and the use of more advanced detectors. These developments are in progress. At present, it cannot be seen how to increase the energy range, other than with the use of a longer crystal monochromator.

University of Southampton
Mathew, Rebecca Jane
2655cef7-7143-42bd-bcc8-cff7954405d5
Mathew, Rebecca Jane
2655cef7-7143-42bd-bcc8-cff7954405d5

Mathew, Rebecca Jane (2001) Towards time resolution in EXAFS of fuel cell electrocatalysts. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Mechanistic and kinetic investigations of fuel cell reactions in real time has not been possible with the conventional XAS technique due to the protracted data collection time. Synchrotron instrumentation improvements have reduced the data collection time to minutes with QuEXAFS and installation of a bent crystal monochromator allows the entire data range to be collected simultaneously with EDE.

In situ X-ray absorption spectra of Pt/C electrodes were collected by conventional XAS, QuEXAFS, and EDE techniques, and are compared; data collection times were 40 mins, 60 s, and 1.9 s respectively. Conventional and QuEXAFS spectra were of similar data quality whereas EDE data exhibited a significant increase in the noise and a decrease in resolution. A shortened data range from k = 17 Å-1 for conventional data to 13 Å-1 for QuEXAFS, and 9 Å-1 for EDE causes an artificial decrease in the calculated coordination numbers. It was concluded that QuEXAFS and EDE would not lead to accurate calculated structural parameters.

Further modifications to the beamline improved the signal to noise ratio and resolution of QuEXAFS and EDE spectra. QuEXAFS therefore replaced conventional XAS since the data was comparable in quality and took a third of the time to collect. The data range of EDE spectra was extended to k = 14 Å-1 and a new PC system allowed for faster and structural parameters. Subsequently, it was concluded that future developments are required on the beamline to increase the signal to noise ratio of the data collected and increase the energy range available. The signal to noise ratio may be improved with a higher energy beam and the use of more advanced detectors. These developments are in progress. At present, it cannot be seen how to increase the energy range, other than with the use of a longer crystal monochromator.

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Published date: 2001

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Local EPrints ID: 464321
URI: http://eprints.soton.ac.uk/id/eprint/464321
PURE UUID: c50b95d1-f35d-4a88-a9df-96d4fcdff9dc

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Date deposited: 04 Jul 2022 22:07
Last modified: 16 Mar 2024 19:25

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Author: Rebecca Jane Mathew

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