Virtual Material Design of PEM Fuel Cell Layers.
Jürgen Becker, Andreas Wiegmann
Fraunhofer ITWM, Kaiserslautern, Germany
The membrane electrode assembly (MEA) of a PEM fuel cell usually consists of 5
layers: cathode gas diffusion layer (GDL), cathode catalyst layer, membrane,
anode catalyst layer and anode GDL. Additionally, a micro-porous layer (MPL)
may be added between GDL and catalyst layer.
Improving the performance of the cell is possible by improving the cell as a
whole, and also by optimizing each of the layers to its requirements. On the
one hand, one should choose the material with the best chemical properties.
On the other hand, as material connectivity and pore morphology have a major
impact on the properties of porous media, improving the microstructure of each
layer is equally important. Finding the best microstructure experimentally is
often too costly or not possible, because any change would require changes in
the production process. Computer simulations help to determine the effective
material properties of a layer without the need to produce it first.
Therefore, in this talk we will present methods to create micro-structural models
of catalyst layer, MPL and GDL. Using these models, one can predict effective
properties of the layers, e.g. permeability, diffusivity, electric conductivity
and thermal conductivity. This is done by solving the appropriate partial differential
equations on the micro-structural model. E.g. the Stokes equation needs to be
solved in order to obtain the effective permeability of the layer.
This approach allows comparing various structural designs.
To validate the approach, we also compare experimentally measured GDL properties
with numerically determined properties. For this purpose, a tomography image of
the GDL is used as model to ensure micro-structural similarity between
experiment and simulation.
Last modified: Fri Oct 22 09:36:15 W. Europe Standard 2010