Effect of current density on membrane degradation under the combined chemical and mechanical stress test in the PEMFCs.

This study elucidates the effects of current density on membrane degradation under combined mechanical and chemical stress tests. Relative humidity (RH) cycling tests using hydrogen gas and air are conducted on a polymer electrolyte membrane fuel cell based membrane NRE211 at the open circuit voltage (OCV), 0.05 and 0.3 Acm−2 conditions. The different current density conditions result in different in-plane membrane stresses and H 2 O 2 formation rates during the test. After every 200 RH cycles, membrane integrity is assessed via the hydrogen crossover rate and OCV. Furthermore, catalytic combustion is analyzed during OCV measurement using a thermal imaging method employing high-transmittance glass at the cathode side. The membrane failed after 1600, 1800, and 2200 RH cycles under the OCV condition, 0.05 of 0.3 Acm−2, respectively. The vigorous membrane degradation under OCV conditions can be attributed to higher mechanical stress and H 2 O 2 formation rate. Hotspots created owing to the combustion between the crossover hydrogen and air were successfully captured, with a maximum temperature rise ranging from 15 to 16 °C compared with a given cell temperature of 80 °C. Moreover, a post-mortem analysis (SEM imaging) revealed the presence of pinholes, through-membrane cracks, and membrane thinning at the hotspot locations. • RH cycling tests are conducted under OCV, 0.05 Acm−2 and 0.3 Acm−2 conditions. • Different conditions cause different mechanical stress and H 2 O 2 formation rates. • Visualization of in-situ catalytic combustion using a high transmittance glass (ZnS). • RH cycling test at lower current density leads to higher stresses on the membrane. • Hotspots emerge at the locations where fatal cracks and pinholes exist. [ABSTRACT FROM AUTHOR]