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@PHDTHESIS{Borowec:1015631,
author = {Borowec, Julian Manuel},
othercontributors = {Hausen, Florian and Wessling, Matthias and Mayer, Joachim},
title = {{M}echanics and electrics of electrolyzer materials - a
micro- and nanoscale analysis},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-06489},
pages = {1 Online-Ressource},
year = {2025},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2025},
abstract = {Understanding Proton Exchange Membrane Electrolyzer Cell
(PEMEC) aging is essential for durability enhancement and
thus competitive electrochemical hydrogen production.
Therefore, the catalyst layers of a long-term operated
(>5000 h) web-woven fiber reinforced Membrane Electrode
Assembly (MEA) were investigated using nanomechanical and
nanoelectrical Atomic Force Microscopy (AFM) techniques,
nanoindentation, and Microscopic Four-Point Probe (μ4PP)
and Macroscopic Four-Point Probe (Ma4PP) analysis.
Reinforcement fibers locally increase the stiffness and
hardness and proved to be suitable for long-term operation.
Nanoindentation reveals an increased Reduced Modulus and
hardness with operation, accompanied by a stiffening of the
near-surface catalyst shown by AFM. This effect is promoted
by a loss of low-stiffness ionomer, confirmed by the
increase of electrically conductive anode surface area. The
most significant anode aging effects were observed only at a
small surface fraction — at certain Porous Transport Layer
(PTL) related domains. Compared to the anode, only minor
aging was observed at the cathode. Micrometer-sized ionomer
plateaus exhibit a stable nature upon operation, as their
stiffness and frequency on the surface remained constant.
The catalyst slightly stiffened at positions within and
outside of Carbon Fiber (CF) PTL imprints, indicating no
influence of the local PTL compression on the aging. While
most PEMEC utilize a cathodic PTL with microscale CFs,
Carbon Nanofiber (CNF) networks are a potential
next-generation PTL material, especially for the Anion
Exchange Membrane Electrolyzer Cell (AEMEC). To tailor the
overall macroscopic electrical properties of
Polyacrylonitrile (PAN)-based CNF networks, microelectrical
and nanoelectrical properties of CNFs, carbonized at
temperatures from 600 °C to 1000 °C, are studied by
conductive AFM. At the microscale, the CNF networks show
good electrical interconnections enabling a homogeneously
distributed current flow. Strikingly, nanoscale current maps
of individual CNFs reveal a large high-resistive surface
fraction, representing a clear limitation. High-resistive
surface domains are either attributed to disordered
high-resistive carbon structures at the surface or the
absence of electron percolation paths in the bulk volume.
With increased carbonization temperature, the conductive
surface domains grow in size resulting in a higher
conductivity. This thesis enhances the understanding of
PEMEC catalyst layer aging related to reinforcement fibers
and PTLs, revealing aging phenomena especially at anode-PTL
related interfaces. Moreover, next generation CNF PTLs were
electrically analyzed. Therefore, this work also contributes
to existing micro-structural models of CNFs by extending
them with electrical properties, especially electron
percolation paths.},
cin = {155630 / 150000},
ddc = {540},
cid = {$I:(DE-82)155630_20160407$ / $I:(DE-82)150000_20140620$},
pnm = {BMBF 03HY122D - Verbundvorhaben $H2Giga_TP_DERIEL:$
De-Risking PEM Elektrolyseur: Teilprojekt der RWTH Aachen:
Alterungserscheinungen und Integration in Upstream- und
Downstreamprozesse (03HY122D) / HITEC - Helmholtz
Interdisciplinary Doctoral Training in Energy and Climate
Research (HITEC) (HITEC-20170406) / DFG project
G:(GEPRIS)390919832 - EXC 2186: Das Fuel Science Center –
Adaptive Umwandlungssysteme für erneuerbare Energie- und
Kohlenstoffquellen (390919832) / iNEW2.0 - Verbundvorhaben
iNEW2.0: Im Zentrum des Inkubators Nachhaltige
Elektrochemische Wertschöpfungsketten (iNEW 2.0) steht die
Erforschung und Entwicklung neuartiger und leistungsfähiger
Elektrolyse-verfahren zur Anwendung in nachhaltigen
Power-to-X (P2X) Wertschöpfungsketten. (BMBF-03SF0627A) /
Doktorandenprogramm (PHD-PROGRAM-20170404)},
pid = {G:(BMBF)03HY122D / G:(DE-Juel1)HITEC-20170406 /
G:(GEPRIS)390919832 / G:(DE-Juel1)BMBF-03SF0627A /
G:(DE-HGF)PHD-PROGRAM-20170404},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-06489},
url = {https://publications.rwth-aachen.de/record/1015631},
}
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