The settling behavior of the carbon based gas diffusion layer in PEM fuel cells

Sammanfattning

This thesis investigate how the Gas diffusion layer in Proton Exchange MembraneFuel Cells settle when exposed to mechanical compression with cyclic load of 4.5 MPaand 7 MPa. A Zwick Roell material tester was used to carry out the mechanicaltesting. 3 different state of the art gas diffusion layers was examined, they arereferred to as GDL "A", "B" and "C" in this report. Three different tests werecarried out, the first with 10 cycle loading, with the load hold time of 60 s. Thesecond test was a 10 cycle loading test as well, but with the load hold time of 60 min.The third test was a 50 cycle loading, with 60 s hold. Images in a Sweeping ElectronMicroscope was also taken, to evaluate the fiber structure in the GDLs. The initialreason was to evaluate the fiber structure before and after compression, this methodwas abandoned, but the images still presented us with some valuable informationabout the different structures of the GDLs and could be used to discuss the results.The results imply that the load hold time effects the settling, and also confirmsprevious research about the so called hysteresis effect where the first loading cycleis the most damaging to the GDL structure. Further on, the 50 cycle testing showthat the settling of the GDLs continues after 10 cycles and more load testing, bothcyclic and static, is of interest in future research.