Influence of dispersion media on Nafion® ionomer distribution in proton exchange membrane fuel cell catalyst carbon support

Interface between the Nafion® ionomer on the high surface area carbon used as catalyst support in the polymer electrolyte membrane fuel cell (PEMFC) electrodes has been studied through a combination of microscopic, spectroscopic and electrochemical techniques. Different support/ionomer interface structures have been developed by varying the dispersion media for ink preparation while keeping the solid composition of the ink invariant. Structural characterizations such as elemental mapping, thermogravimetric analysis and Raman/Infrared spectroscopy of the dried inks reveal significant impact of the dispersion media on the distributions of the ionomer/support phases. Further, variation of the double layer capacitance (DLC) of the ionomer/support inks coated on gold electrodes with the scan rate during cyclic voltammetry measurements has been studied to evaluate the ionomer/support interface performance. Substantial impact of the dispersion media has been observed on the scan rate/DLC profiles for the inks. Low ratios of the DLC values at scan rates of 1000 and 100 mV/s have been observed for the ionomer/carbon support inks having partially inhomogeneous ionomer/carbon distribution. Finally, infrared spectroscopy suggested different interactions of the –SO3 group with the support carbon for the inks prepared using different types of dispersion media.