Understanding fibre architecture for better performing PEM fuel cells
Hydrophobic polymers are used in fuel cells to distribute reactant gases and remove water. Researchers have mapped the hydrophobic polymers on a micrometre scale, and the findings show how the distribution and the underlying fibre structure affect both performance and durability. This knowledge can lead to new design strategies for improved fuel cells.
In fuel cells hydrogen molecules are split into protons and electrons to produce electrical power. For this process many fuel cells have a proton exchange membrane (PEM) that allows protons to pass through, while the electrons are forced to travel via an external circuit.
PEM fuel cells have low operating temperatures, high efficiency and scalability across different applications. At the same time, they rely on carefully engineered materials and are sensitive to design choices. The use of precious‑metal catalysts and specialised polymer components means that performance losses or degradation can quickly become costly.
A balancing act between gas distribution and water management
One crucial component in a PEM fuel cell is the gas diffusion layer (GDL) which is a porous carbon structure that distributes reactant gases evenly while also enabling excess water to be removed from the cell. This process is a delicate balance between permeability and water management, and GDLs are therefore commonly modified with hydrophobic polymers.
Dylan Schulz is a PhD student at Chalmers University of Technology involved in the SESBC project “Towards a more efficient use of fuel cells and electrolysers”, and the main author of the recently published paper "The Role of Native Binder in Controlling the Polytetrafluoroethylene Distribution in Gas Diffusion Layers for Proton Exchange Membrane Fuel Cells".
“By using a combination of advanced imaging methods, including Raman spectroscopy, electron microscopy and X‑ray analysis we have mapped the distribution of the hydrophobic polymer at identical locations inside different commercial GDL materials. We can show that the critical factor is not only how much of this material is added, but how it is distributed within the GDL structure,” Dylan explains.
Fibre microstructure affects performance
The carbon structure in GDLs can be can be manufactured with or without a binding material. In GDLs without a binding material the polymer tends to accumulate at fibre junctions which are essential regions for gas transport, and this blockage increases resistance to oxygen. When there is a binding material present in the GDL the polymer instead tends to accumulate between the fibres where it has a much smaller impact on transport pathways of the gas.
“Differences in polymer distribution influence oxygen transport, but the findings suggest that the underlying fibre structure itself plays an even more important role in determining fuel cell performance,” says Dylan.
The study highlights the importance of the GDL microstructure in governing transport processes inside the cell. By understanding how the fibre architecture influences both gas transport and the distribution of hydrophobic materials, it opens up new design strategies to improve fuel cell performance and durability.
“Although at first sight, these insights may not seem relevant for the system level, they are essential for making hydrogen technologies reliable and economically viable. By connecting microscopic structure to macroscopic performance, this research brings fuel cell engineering one step closer to large‑scale deployment,” says Anna Martinelli, senior author of the study, and project leader of “Towards a more efficient use of fuel cells and electrolysers”.
Licentiate defence
Dylan Schulz will defend his licentiate thesis on 3 Sep, 10:00 – 11:00, Kemi-Life Room 10050 Viva at Chalmers University of Technology: