Enhanced chemical durability of polymer electrolyte membrane fuel cells by crown ether grafted carbon nanotube

Low chemical stability of membrane-electrode assembly (MEA) remains a major obstacle to commercialization of polymer electrolyte membrane fuel cells (PEMFCs) for fuel cell electric vehicles (FCEVs). In this study, we doubly anchored cerium-ion in the catalyst layer by forming a complex with the 15-crown-5-ether and additionally grafting to the multiwall carbon nanotube (Ce/CRE-graft-CNT) as a long-lasting radical scavenger. To confirm the effect of Ce/CRE-graft-CNT on chemical durability, the binding energy between the cerium-ion and crown ether was identified with DFT calculations. The incorporation of Ce/CRE-graft-CNT into catalyst layer decreases decay rate of open circuit voltage (OCV) by 4 times from 2.13 to 0.56 mV h⁻¹ for 210 h operation. The performance retention of the Ce/CRE-graft-CNT (70.8 %) at 0.6 V is also higher than that of the Ce/CRE-blend-CNT (44.8 %). The results indicate that the doubly anchored Ce/CRE-graft-CNT has a more retention capability as a radical scavenger. Therefore, a tightly bounded cerium-ion/crown ether complex with CNT can provide a strategy to improve the chemical durability of MEAs.