TY  - JOUR
A1  - Tötzke, Christian
A1  - Gaiselmann, G.
A1  - Osenberg, M.
A1  - Arlt, T.
A1  - Markötter, H.
A1  - Hilger, A.
A1  - Kupsch, Andreas
A1  - Müller, B. R.
A1  - Schmidt, V.
A1  - Lehnert, W.
A1  - Manke, Ingo
T1  - Influence of hydrophobic treatment on the structure of compressed gas diffusion layers
JF  - Journal of power sources : the international journal on the science and technology of electrochemical energy systems
N2  - Carbon fiber based felt materials are widely used as gas diffusion layer (GDL) in fuel cells. Their transport properties can be adjusted by adding hydrophobic agents such as polytetrafluoroethylene (PTFE). We present a synchrotron X-ray tomographic study on the felt material Freudenberg H2315 with different PIPE finishing. In this study, we analyze changes in microstructure and shape of GDLs at increasing degree of compression which are related to their specific PTFE load. A dedicated compression device mimicking the channel-land pattern of the flowfield is used to reproduce the inhomogeneous compression found in a fuel cell. Transport relevant geometrical parameters such as porosity, pore size distribution and geometric tortuosity are calculated and consequences for media transport discussed. PTFE finishing results in a marked change of shape of compressed GDLs: surface is smoothed and the invasion of GDL fibers into the flow field channel strongly mitigated. Furthermore, the PTFE impacts the microstructure of the compressed GDL. The number of available wide transport paths is significantly increased as compared to the untreated material. These changes improve the transport capacity liquid water through the GDL and promote the discharge of liquid water droplets from the cell. (C) 2016 Elsevier B.V. All rights reserved.
KW  - Gas diffusion layer
KW  - Synchrotron tomography
KW  - Compression
KW  - Hydrophobic treatment
KW  - Water transport
Y1  - 2016
U6  - https://doi.org/10.1016/j.jpowsour.2016.05.118
SN  - 0378-7753
SN  - 1873-2755
VL  - 324
SP  - 625
EP  - 636
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Fazeli, Mohammadreza
A1  - Hinebaugh, James
A1  - Fishman, Zachary
A1  - Tötzke, Christian
A1  - Lehnert, Werner
A1  - Manke, Ingo
A1  - Bazylak, Aimy
T1  - Pore network modeling to explore the effects of compression on multiphase transport in polymer electrolyte membrane fuel cell gas diffusion layers
JF  - Journal of power sources : the international journal on the science and technology of electrochemical energy systems
N2  - Understanding how compression affects the distribution of liquid water and gaseous oxygen in the polymer electrolyte membrane fuel cell gas diffusion layer (GDL) is vital for informing the design of improved porous materials for effective water management strategies. Pore networks extracted from synchrotron-based micro-computed tomography images of compressed GDLs were employed to simulate liquid water transport in GDL materials over a range of compression pressures. The oxygen transport resistance was predicted for each sample under dry and partially saturated conditions. A favorable GDL compression value for a preferred liquid water distribution and oxygen diffusion was found for Toray TGP-H-090 (10%), yet an optimum compression value was not recognized for SGL Sigracet 25BC. SGL Sigracet 25BC exhibited lower transport resistance values compared to Toray TGP-H-090, and this is attributed to the additional diffusion pathways provided by the microporous layer (MPL), an effect that is particularly significant under partially saturated conditions. (C) 2016 Elsevier B.V. All rights reserved.
KW  - Pore network modeling
KW  - Synchrotron X-ray
KW  - Computed tomography
KW  - Liquid water distribution
KW  - Gas diffusion layer
KW  - Compression
Y1  - 2016
U6  - https://doi.org/10.1016/j.jpowsour.2016.10.039
SN  - 0378-7753
SN  - 1873-2755
VL  - 335
SP  - 162
EP  - 171
PB  - Elsevier
CY  - Amsterdam
ER  -