Phase-change-related degradation of catalyst layers in proton-exchange-membrane fuel cells

Understanding and optimizing water and thermal management in the catalyst layer of proton-exchange-membrane fuel cells is crucial for performance and durability improvements. This is especially the case at low temperatures, where liquid water and even ice may exist. In this article, the durability of a traditional Pt/C dispersed and a nanostructure thin film (NSTF) membrane-electrode assembly (MEA) are examined under wet/dry and freeze/thaw cycles using both in situ and ex situ experiments. Multiple isothermal cold starts result in a performance degradation for the dispersed MEA, while no such a degradation is found in the NSTF. The results are consistent with stand-alone MEA tests, wherein the dispersed catalyst layer results in an exponential increase in the number and size of cracks until it delaminates from the membrane due to the impact of the freeze/thaw process within the catalyst-layer pores. The NSTF catalyst layer shows minimal crack generation without delamination since the ice forms on top of the layer. The results are useful for understanding degradation due to phase-change containing cycles.