Stability of SPEEK/Cloisite®/TAP nanocomposite membrane under Fenton reagent condition for direct methanol fuel cell application

The stability of SPEEK/Cloisite®/triaminopyrimidine (SP/CL/TAP) nanocomposite membrane against radical attack during DMFC operation was elucidated by the Fenton reagent test. The nanocomposite membrane was soaked in the Fenton reagent solution with 0.8-50 ppm iron salts concentration for up to 96 h. The results indicate that presence of Cloisite® inorganic particles can improve the stability of SP/CL/TAP nanocomposite membrane against the radical attack. FT-IR characterization combined with DFT study has shown that C‒O‒C and ‒SO3H bonding with phenylene ring, and hydrogen bonding between SPEEK, Cloisite®, and TAP are vulnerable to the radical attack. Loss of these functional groups has caused structural deformation, deterioration of mechanical strength, and changes of hydrophilicity in the SP/CL/TAP nanocomposite membrane. Additionally, changes in its chemical structure have caused its water uptake, proton conductivity, and methanol barrier properties to drop, up to 2 × higher than the Nafion® 117 membrane. However, the selectivity value of the SP/CL/TAP nanocomposite membrane (27,037 S∙s/cm3) remains higher than the Nafion® 117 membrane (3292 S∙s/cm3) due to its lower methanol permeability value (2.72 × 10−7 cm2/s) as compared to Nafion® 117 membrane (2.95 × 10−6 cm2/s). Based on the correlation graph, the SP/CL/TAP nanocomposite membrane could operate as PEM in the DMFC system up to 9800 h. Based on the results, it can be concluded that the SP/CL/TAP nanocomposite membrane has good stability in DMFC harsh environment and suitable to be employed as PEM for high-performance and long lifespan DMFC system.