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- Resolution neutron-radiography (2)
- Cells (1)
- Gas diffusion layer (GDL) (1)
- Gas diffusion layers (1)
- Gas-diffusion layers (1)
- HT-PEFC (1)
- Local current distribution (1)
- Membrane electrode assembly (MEA) (1)
- PEMFC (1)
- Phosphoric acid (1)
The three-dimensional water distribution and water transport paths in the gas diffusion layer (GDL) and the adjacent micro-porous layer (MPL) of a polymer electrolyte membrane fuel cell (PEMFC) were analyzed during cell operation. The technique of quasi in-situ X-ray tomography was used for a 3D visualization of the water distribution and the structure of the GDL at different operating conditions. Based on findings from in-situ radiographic measurements water transport paths were detected and subsequently examined by tomography. The combination of these 2D and 3D techniques allows for a fully three-dimensionally resolved visualization of transport paths through the GDL.
Synchrotron X-ray radiography and tomography investigations of a custom-made polymer electrolyte membrane fuel cell optimised for visualisation purposes are presented. The 3D water distribution and transport pathways in the porous carbon fibre gas diffusion layers (GDLs) were investigated. The authors found that water is not only moving from the GDL into the channel, but can also take the opposite way, that is, from the channel into free pore space of the GDL. Such movement of water into the opposite direction has been subject of speculations but has so far not yet been reported and might bring new insights into the general water transport behaviour, which might give new aspects to the general description of water transport processes and influence modelling assumptions to describe the process taking place in the GDL.
Investigation of fuel cell materials and liquid water transport by means of synchrotron imaging
(2013)
Synchrotron imaging allows addressing various important issues in fuel cell research, for example water distribution and transport. The water distribution in polymer electrolyte membrane fuel cells (PEMFCs) was observed quasi in-situ directly after operation by means of synchrotron tomography. The 3D data set was compared with the tomogram of a dry cell in order to separate the water distribution from cell materials. Engineered transport pathways realized by perforating holes through the gas diffusion layer (GDL) are a recent approach to optimize water transport and cell performance. For some parameter sets a cell performance increase and an improvement of stabilization have already been proven. We present high resolution investigations of the water distribution in perforated GDLs of operating PEMFCs by means of in-situ synchrotron radiography. The surrounding areas of the holes exhibited a distinct hydrophilic character.
In contrast to classical low temperature polymer electrolyte fuel cells (LT-PEFCs), the membrane conductivity in high temperature polymer electrolyte fuel cells (HT-PEFCs) (operating temperature ~ 160 °C) is based on proton transport within phosphorus-oxygen acids at different levels of hydration, orthophosphoric acid (H3PO4) being the simplest example. We present for the first time in-situ synchrotron X-ray radiography measurements applied to a HT-PEFC to gain insight into the local composition of the membrane electrode assembly (MEA) under dynamic operating conditions. Transmission changes during the radiographic measurements exhibit a clear influence of the formation of product water on the membrane composition.