Effect of open circuit voltage on degradation of a short proton exchange membrane fuel cell stack with bilayer membrane configurations

In the present work, membrane electrode assembly degradation of a 4-cell stack with specially designed twin catalyst coated membranes (twin-CCMs) was carried out for 1600 h under open circuit voltage (OCV) conditions. Four types of membrane with various thicknesses were employed in the experiment. Each twin-CCM was composed of two membranes of the same type with a catalyst layer coated only on one side. The purpose of this special configuration was to facilitate postmortem analysis of the membrane after degradation due to the detachable membrane structure. By means of several in situ electrochemical measurements, the performance of the individual cells was analysed every 200 h during the degradation process. Postmortem analyses such as scanning electron microscopy, atomic force microscopy, and infrared imaging were also conducted to identify the membrane degradation mechanisms after exposure to OCV. The results indicate that membrane degradation, which correlates with electrode degradation, is the most direct reason for the failure of the whole cell/stack during OCV operation, especially for cells with thinner membranes.

► Accelerated test on a PEM fuel cell stack at open circuit condition was reported.
► The stack featured detachable twin-CCM configuration for postmortem analyses.
► SEM detection indicated a stronger thinning at the cathode side than the anode side.
► AFM study revealed that the aged inner membrane surfaces were significantly stiffer.