Hetero‐Interface Maximized UiO‐66‐NH 2 /CeO 2−x Free Radical Scavenging Additives for Long‐Term Operation of Proton Exchange Membrane Fuel Cells
Jinwon Choi, Do Hyeon Jang, Jeonghyeon Kim, Ji Hyo Kim, Seojin Yoo, Taekyung Kim, Hionsuck Baik, Ji Yeong Lee, Sangwon Kim, Dong‐Ku Kang, Dong Won Kang, Jin Young Kim, Taehyun KwonABSTRACT
The long‐term durability of proton exchange membrane fuel cells (PEMFCs) remains a critical hurdle for their widespread commercialization, largely because of chemical degradation of the membrane electrode assembly (MEA) by unintentionally generated free radicals during operation. Defective ceria (CeO 2−x ) nanoparticles have emerged as promising radical‐scavenging additives through reversible Ce 3+ /Ce 4+ redox cycling. However, their radical scavenging efficiency is limited by the sluggish regeneration of surface Ce 3+ species, which are the active species for radical scavenging, leading to a gradual loss of their initial scavenging capability during long‐term cell operation. Here, we report a strategy to accelerate Ce 3+ regeneration kinetics by maximizing heterointerface‐derived interactions through simple seed‐mediated growth of defective ceria on the surface of a metal‐organic framework (MOF). In particular, UiO‐66‐NH 2 undergoes partial amorphization and dissolution during the CeO 2−x nanoparticle growth, which enables intimate interfacial contact and enhanced electronic coupling with CeO 2−x . The resulting UiO‐66‐NH 2 /CeO 2−x heterostructure exhibits improved redox cycling and higher Ce 3+ retention under oxidative conditions than commercial ceria nanoparticles. Moreover, when incorporated into the cathode catalyst layer of the MEA, the UiO‐66‐NH 2 /CeO 2−x significantly suppressed the performance degradation, enabling stable single‐cell operation for over 500 h under an accelerated durability test.