Cross-linker effect in ETFE-based radiation-grafted proton-conducting membranes II. Extended fuel cell operation and degradation analysis

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Official URL: http://dx.doi.org/10.1149/1.3082109

In this study the effect of crosslinker (divinylbenzene (DVB)) content on the chemical stability of poly(ethylene-alt-tetrafluoroethylene) (ETFE) based membranes using an H2O2 solution was carried out. Furthermore, the first long term-testing of single H2/O2 cell over 2180h of an MEA assembled using an optimized ETFE-based membrane prepared by radiation-induced grafting of styrene / DVB and subsequent sulfonation with a graft level of 25 % was carried out. The in situ MEA properties were characterized over the testing period using auxiliary current-pulse resistance, electrochemical impedance spectroscopy, polarization and H2 permeation. It is shown that the crosslinking dramatically improves the ex situ chemical stability, while no significant trend with the crosslinker content was observed. The performance of the tested MEA exhibits a decay rate of 13 μV.h-1 in voltage over the testing time at 500 mA.cm-2 at 80°C, while the hydrogen permeation shows a steady increase over time. This indicates clearly that to some extent changes in the membrane morphology occur over the operating time. The local post mortem analysis of the tested membrane reveals that high degradation was observed in areas adjacent to the O2 inlet and in other areas nearby