Nanostructure-transportation relation to PEMFCs activity and durability degradation

The Proton exchange membrane (PEM) is a crucial component in the membrane electrode assembly (MEA), playing a vital role in providing a channel for water transport and acting as a bridge for proton conduction. However, during the long-term operation of fuel cells, PEM is susceptible to attack from metal ions such as Cr 3+ originating from the corrosion of metallic bipolar plates , leading to changes in its transport properties. Here, we report on the impact of Cr 3+ on the microstructure and mechanical properties of PEM and then correlate it with changes in water uptake and proton conductivity , studying the effect of Cr 3+ contamination on fuel cell performance and durability. The study reveals that Cr 3+ forms a dense cross-linking structure with sulfonic acid groups inside the ionomer , resulting in an increase in storage modulus due to the larger ion radius and higher valence state, leading to a decrease in water uptake and proton conductivity. The membrane transport properties are primarily dependent on its water content. It is observed that Cr 3+ contamination reduced the fuel cell voltage and maximum power density by 47.6 % and 57.1 %, respectively, with a voltage attenuation rate up to 2.9 mV/h, nearly 14 times that of the uncontaminated condition (0.21 mV/h). These findings provide valuable insights for developing high-transmission PEMs and aid in predicting the degradation and lifespan of fuel cells under actual operating conditions.