Understanding of free radical scavengers used in highly durable proton exchange membranes

Nafion/Surface Modified Ceria Hybrid Membranes for Fuel Cell Application

“…These radicals cause proton-exchange membranes to degrade and decrease FC power [10][11][12][13]. Cerium ions can interact with reactive oxygen species due to the reversible redox reaction Ce 4+ ↔ Ce 3+ [14][15][16][17]. Cerium ions can be introduced into the membrane matrix by ion-exchange [18,19] or by casting of the membrane solution with previously prepared CeO 2 nanoparticles [20][21][22].…”

Ceria nanorods as highly stable free radical scavengers for highly durable proton exchange membranes

“…FRSs in PEMs are quenchers of free radicals, and chemical degradation of PEMs is relieved via the reaction between FRSs and free radicals. 13 FRSs based on metal oxides are the most commonly used materials in PEMs, especially ceria, which has polyvalent cerium ions on the surface. Ceria can react with free radicals via the mechanism in Fig.…”

Reinforced Composite Membranes Based on Expanded Polytetrafluoroethylene Skeletons Modified by a Surface Sol–Gel Process for Fuel Cell Applications

“…As the most popular PEMs in PEMFCs, perfluorosulfonic acid (PSFA) membranes, particularly Nafion (Dupont Co.), are widely used by virtue of their favorable conductivity and suitable mechanical strength. , Nevertheless, this type of membrane suffers from critical mechanical and chemical degradations during long-term service. ,, Their chemical failure is mainly manifested through membrane thinning attributed to the ionomer exposure in severe radical environments [hydrogen peroxide (H 2 O 2 ), hydroxyl (HO*), and hydroperoxyl (HOO*)]. ,− The attenuation of membrane thickness may result in a reduction in functional sulfonic groups and the exacerbation of reactant crossover, ultimately resulting in performance degradation of the fuel cells. ,, In contrast, their mechanical failure is predominantly reflected by the structural deterioration of the PSFA membrane (e.g., cracks, wrinkles, pinholes, and tears). ,, A major contributing factor causing mechanical failure is the excessive repeated swelling and shrinking of the membranes under humidity cycling conditions. ,, This phenomenon can be attributed to the inferior dimensional stability of PSFA ionomers under alternating dry and wet atmospheres, and it results in irreversible defects in the membrane bulk …”