High-temperature PEM fuel cell electrode catalyst layers Part 2: Experimental validation of its effective transport properties

In this study, the experimental approach for determination of high-temperature PEM fuel cell, PBI-bonded catalyst layer conductivity and transfer properties was developed and optimised. Electrical conductivity was determined by chronopotentiometry combined with mathematical model, using uncompressed catalyst layer on a conductive glass support. Effective transport properties were determined using gas-diffusion electrode samples fixed in the Wicke-Kallenbach cell. Experimental results were compared with quantities calculated from FIB-SEM tomography. Very good agreement between the results was reached. Theoretical data evaluated on the base of tomography may thus be considered as validated. The results confirm the heat treatment of the catalyst layer to lead to its reorganisation to less porous and better-defined structure with improved electrical conductivity. Changes in effective transport properties, however, were not pronounced. This is due to the nature of gas diffusion electrode samples. Determined electrical conductivities and transfer properties of catalyst layer underlined the importance of gas-diffusion electrode preparation procedure. This represents an important input for further studies, focused on optimisation of membrane-electrode assemblies for HT PEM FC.