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@PHDTHESIS{Liu:771032,
author = {Liu, Shuai},
othercontributors = {Lehnert, Werner Karl Josef and Singheiser, Lorenz},
title = {{M}orphology and degradation of high temperature polymer
electrolyte fuel cell electrodes},
volume = {479},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH, Zentralbibliothek, Verlag},
reportid = {RWTH-2019-09902},
series = {Schriften des Forschungszentrums Jülich. Reihe Energie
$\&$ Umwelt = Energy $\&$ environment},
pages = {1 Online-Ressource (III, 162 Seiten) : Illustrationen,
Diagramme},
year = {2019},
note = {Auch veröffentlicht auf dem Publikationsserver der RWTH
Aachen University; Dissertation, RWTH Aachen University,
2019},
abstract = {The polybenzimidazole-based high-temperature polymer
electrolyte fuel (HT-PEFC) has become a major topic in the
clean energy field in recent years due to the appealing
advantages, e.g., improved electrochemical kinetics and
enhanced tolerance to carbon monoxide. However, the
introduction of phosphoric acid (PA) in the membrane
electrode assembly (MEA) leads to several issues, e.g.,
phosphate contaminations, accelerated Pt corrosion, and PA
leaching. What is more, compared to classic PEFCs, the
required higher Pt loading is another factor that impedes
the commercialization of HT-PEFCs. The dissertation focuses
on the electrochemical processes in the MEA, especially on
the cathode side, to investigate the relations among the
parameters of the MEA as well as study the degradation
mechanism under different operating conditions. Various
types of gas diffusion electrodes are fabricated by using
different methods and recipes. Electron characterizations
and electrochemical measurements demonstrate that the
electrodes with more regular cracks and less PTFE
agglomerations perform better. The PTFE binder plays a role
in adjusting the PA distribution in the MEA and 10-25
$wt.\%$ PTFE is the advised content in the cathodecatalyst
layer (CCL). In addition, the interactions of another three
parameters in MEAs (i.e., Pt loading, thickness of CCL, and
PA doping level) are investigated by using the design of
experiment (DoE) method. The results propose a direction for
the preparation of MEAs: a relatively high PA doping level
and a low ratio of Pt/C catalyst are beneficial to improve
the Pt utilization efficiency inHT-PEFCs. The degradation in
HT-PEFCs is another emphasis of this dissertation. Five
stressors that include high temperature, open circuit
voltage, thermal cycling, low-load cycling and high-load
cycling areapplied to the above optimized MEAs. A Pt band is
unexpectedly visualized in the membrane of an MEA only run a
standardized break-in procedure by using the focused ion
beam milling technique. This concretely proves the corrosive
environment in HT-PEFCs. The Pt band formation is explicitly
influenced by the operating conditions. The OCV and low-load
cycling stressors cause the largest amount of Pt loss into
the membrane, indicating that the high potential is the most
pronounced factor in Pt corrosion. During the aging tests,
the membrane degradation and PA leaching only have minor
effects on the performance loss, while the main cause is the
degradation of the Pt/C catalyst.},
cin = {420520},
ddc = {620},
cid = {$I:(DE-82)420520_20140620$},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
doi = {10.18154/RWTH-2019-09902},
url = {https://publications.rwth-aachen.de/record/771032},
}
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