Sandwich-like Nafion composite membrane with ultrathin ceria barriers for durable fuel cells

Improving the durability of the membrane electrode assembly (MEA) while obtaining high performance is required to further commercialize polymer electrolyte membrane fuel cells (PEMFCs). The durability of PEMFCs is improved by incorporating radical scavengers, such as CeO2 (ceria), into the MEA, especially the membrane. However, nanosized ceria particles are generally mixed with ionomers and are cast on substrates to fabricate composite membranes. In such a case, controlling their morphology and avoiding particle agglomeration is difficult. Herein, we report a novel method for constructing a robust membrane by incorporating ultrathin ceria barriers into the outermost sides of a commercial Nafion membrane to effectively alleviate radical attacks while ensuring the high uniformity and controllability of ceria layers. The improved durability of the composite membrane is confirmed via ex situ Fenton's test and in situ operation of a fuel cell. Moreover, we observe that the amount of fluoride ion emission and the loss of proton conductivity of the membranes decrease as the CeO2 density increases. The MEA comprises a modified membrane with CeO2 barriers that show proper areal density. It demonstrates excellent durability under accelerated environmental conditions (open circuit voltage test) and acceptable initial performance with an insignificant decrease in proton conductivity.

Automated summary

Improving the durability of PEMFCs by incorporating radical scavengers such as ceria into the MEA, especially the membrane, is crucial for further commercializing polymer electrolyte membrane fuel cells. A novel method of constructing a robust membrane by adding ultrathin ceria barriers to the outermost sides of a commercial Nafion membrane has been developed, leading to enhanced durability and proper areal density of CeO2 barriers. The decreased amount of fluoride ion emission and loss of proton conductivity with increasing CeO2 density suggest improved performance and durability of the modified membrane.