Methodic Aspects of XPS Depth Profiling for Investigations of Fuel Cell Components

Abstract

The focus of this work is to obtain detailed information about the physical composition of the individual fuel cell components in order to optimize them and increase cell durability. An approach for the ex-situ characterization of fuel cell components, such as gas diffusion media or catalyst layers is by using XPS. In this work, we address methodic aspects of depth profiling of direct methanol fuel cell components (microporous layers and catalyst layers) using adhesive tape peel-off with subsequent XPS analysis. By using this approach, we have successfully demonstrated cross-over of Ru ions and possibly Pt ions from the anodic catalyst to the cathodic catalyst layer and even to the microporous layer. Moreover, our experimental results allow determining where the dissolved catalyst ions redeposit within the membrane electrode assembly. Finally, our findings suggest that cross-over of Pt and Ru ions, observed under different operation conditions, are uncoupled.