Impact of Cell Compression on Resistance, Mass Transport, and Ultimate PEMFC Performance

The gas diffusion layer (GDL) plays multiple roles in the performance of a PEMFC: it provides pathways for fuel transport to and water away from the catalyst layer via the tortuous void/pore structure and it  ensures a good electronic contact between the catalyst layer and the current collector of the PEMFC stack.  A balancing act in cell assembly must be struck for the GDL to simultaneously offer the best transport pathways and electronic contact; different PEMFC operating conditions can require different assembly in terms of compression.  To gain a better understanding of this balancing act and to optimize the performance of the PEMFC, we systematically varied the compression of a single cell PEMFC and evaluated it under different operating conditions to extract the impact on contact resistance and mass transport.  Scanning electron microscopy of the GDL and catalyst layers post mortem reveal changes in the overall pore/void structure and provide further clues on the implications of compression on performance.