Master thesis presentation Frederikke Björklund Larsen, MPMCN

Abstract:
As the world push to lower carbon dioxide emissions to limit climate change, the need for new technologies becomes more and more critical. An emerging technology is hydrogen fuel cells and amongst them are proton exchange membrane fuel cells. With all new technologies there are several factors that need development, and this work takes a closer look at the catalyst layer of the cathode. Setting out to increase the platinum loading in the cathode while at the same time avoiding cracks, several catalyst inks were made with varying dispersion matrices. The matrices explored were a) water with ethanol and 1-propanol (2:2:1 weight ratio), b) water with 1-propanol (2:3 weight ratio), c) water with 2-propanol (2:3 weight ratio), d) water with tert-butanol (2:3 weight ratio), e) water with 1-propanol and tert-butanol (2:1:2 weight ratio), and f) water with 1-propanol and tert-butanol (1:1:3 weight ratio).

To get a deeper understanding of the ink properties, rheological tests of the inks and visual analysis of produced electrodes were performed. These analyses found improved coating quality and a higher viscosity for dispersions having a lower dielectric constant and for inks containing solvent with a lower vapour pressure. The improved behaviour was attributed to improved interactions between the ink’s compounds and slower drying of the coatings, leading to less stresses in the electrodes. An improved electrode quality was also observed when the inks were left to mature on a magnetic stirrer for several days. The maturation step resulted in lower viscosity of the inks indicating smaller effective volume fraction of particles and less electrostatic repulsion and steric hinderance between compounds. A final factor in the process that was tested was increasing the relative humidity during the drying process. Here an improved cracking behaviour was observed for the ink containing more water while the opposite was seen in the ink containing more tert-butanol. These findings point towards the need for specific drying processes to each individual ink.

Examiner: Björn Wickman
Supervisor: Parinaz Mikaeili
Opponent: Rajesh Vishwakarma