Effects of Freezing and Thawing on the Structures of Porous Gas Diffusion Media Available to Purchase

Fuel cells are a very promising technology for transportation applications in the future. Many companies are performing research in order to make the implementation of fuel cell-powered vehicles more feasible. One issue that needs to be addressed is the fact that fuel cell vehicles will be used in sub-freezing climates. Vehicles undergo frequent shut down and startup events, and as such, freezing and thawing effects on fuel cell components become important when the vehicle is stored overnight in cold climates. When shut off, fuel cells will maintain water in the membrane electrode assembly (MEA) and gas diffusion media unless certain purging protocols are adhered to. When the cell is subjected to sub-freezing temperatures, the water remaining in these media will freeze. This freezing could have a detrimental impact on the pore structure, fiber integrity, and binder effectiveness in the GDL, thereby decreasing the electrochemical active surface area of the electrolytes and hurting the overall performance of the cell. This paper details the prior research in the area of freezing and thawing effects in these media and also details current research on the degradation of the GDL specifically.