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.