Scientists get atomistic picture of platinum catalyst degradation

Date:
August 24, 2020
Source:
European Synchrotron Radiation Facility
Summary:
Degradation of platinum, used as a key electrode material in the
hydrogen economy, severely shortens the lifetime of electrochemical
energy conversion devices, such as fuel cells. For the first time,
scientists elucidated the movements of the platinum atoms that
lead to catalyst surface degradation.



FULL STORY ========================================================================== Degradation of platinum, used as a key electrode material in the
hydrogen economy, severely shortens the lifetime of electrochemical
energy conversion devices, such as fuel cells. For the first time,
scientists elucidated the movements of the platinum atoms that lead to
catalyst surface degradation.

Their results are published today in Nature Catalysis.


==========================================================================
For more than half a century, platinum has been known as one of the best catalysts for oxygen reduction, one of the key reactions in fuel cells.

However, it is difficult to meet the catalysts' long-term high activity
and stability needed for the massive deployment of the hydrogen technology
in the transportation sector.

Scientists led by Kiel University (Germany), in collaboration with the
ESRF, University of Victoria (Canada), University of Barcelona (Spain)
and Forschungszentrum Ju"lich (Germany), have now found out why and how platinum degrades. "We have come up with an atomistic picture to explain
it," says Olaf Magnussen, professor at Kiel University and corresponding
author of the article.

In order to achieve this, the team went to ESRF's beamline ID31 to study
the different facets of platinum electrodes in electrolyte solution. They discovered how atoms arrange themselves and move on the surface during
the processes of oxidation, the main reaction responsible for platinum dissolution.

The findings open doors to atomistic engineering: "With this
new knowledge, we can imagine targeting certain shapes and surface
arrangements of nanoparticles to enhance the stability of the catalyst. We
can also find how the atoms move, so we could potentially add surface
additives to suppress atoms moving the wrong way," explains Jakub Drnec, scientist at beamline ID31 and co-author of the study.

The fact that the experiments took place under electrochemical conditions similar to what happens in the actual device was key to translate the
findings into fuel cell technology. "Because platinum surface rapidly
changes during oxidation, these measurements became possible only thanks
to a new, very fast technique for surface structure characterization. This method, high-energy surface X-ray diffraction, has been co-developed
at the ESRF" explains Timo Fuchs, from Kiel University and co-author
of the study. "And it is, in fact, the only technique that can provide
this kind of information in the real environment," he adds. This is the
first publication where atomic movements were determined by the technique
under such conditions.

This research owes its success to the combination of the X-ray
measurements at the ESRF with highly sensitive dissolution measurements performed at Forschungszentrum Ju"lich and advanced computer
simulations. "Only such a combination of different characterization
techniques and theoretical calculations provides a full picture of what
goes on with the atoms at the nanoscale level in a platinum catalyst,"
notes Federico Calle-Vallejo from University of Barcelona, in charge of
the simulations.

The next step for the team is to continue experiments that provide insight
into the degradation mechanisms of further model facets mimicking edges
and corners on catalyst particles. These results will provide a map of
platinum stability under reaction conditions and allow researchers to
develop rational strategies for the design of more stable catalysts in
the future.


========================================================================== Story Source: Materials provided by
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========================================================================== Journal Reference:
1. Timo Fuchs, Jakub Drnec, Federico Calle-Vallejo, Natalie Stubb,
Daniel J.

S. Sandbeck, Martin Ruge, Serhiy Cherevko, David A. Harrington,
Olaf M.

Magnussen. Structure dependency of the atomic-scale mechanisms
of platinum electro-oxidation and dissolution. Nature Catalysis,
2020; DOI: 10.1038/s41929-020-0497-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200824165611.htm

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