Post Mortem Analysis of Degraded DMFC After Extended Operation

Abstract

This work presents an ex-situ analysis of long-term (>1000 h) aged DMFC. Specifically, the data comprise a comparison of pristine, activated and aged MEA components in order to assess the observed physical changes with respect to their impact on permanent performance loss. The components analyzed by means of X-ray photoelectron spectroscopy and electron microscopy are GDLs, MPLs, CLs and membranes. Our results clearly show that Ru cross-over from anode CL to cathode CL and MPL, associated with observation of catalyst precipitates in the membrane, occurs mainly at the beginning of the operation (first 30 h) and proceeds only slowly upon long term aging. Hence, this effect seems to represent a minor contribution to the overall performance loss. In the MPL and CL of the anode and the cathode side a loss of polymers is observed which occurs predominantly at the beginning of operation too. An effect attributed to long-time operation is the gradual chemical decomposition of PTFE (fluorine depletion) especially in the anodic GDL.