Aliphatic-aromatic sulphonated polyimide and acid functionalized polysilsesquioxane composite membranes for fuel cell applications
2013
Pandey, Ravi P. | Shahi, Vinod K.
For the design of highly stable and proton conductive polymer electrolyte membranes (PEM), we synthesized nucleophillic attack resistant sulphonated polyimide (SPI), in which electron-withdrawing sulphonic acid groups were not directly attached through amino-phenyl rings, using diamines with high basicity and dianhydride with low electron affinity. SPI- sulphonated silica precursor (SSP) composite PEM was assessed for its high water activity (water retention capacity) and direct methanol fuel cell (DMFC) applications. SPI/SSP-40 (composite membrane with 40 wt% SSP content) showed 10.25 × 10⁻⁸ cm² s⁻¹ water diffusion coefficient; 1.86 mequiv. per g ion-exchange capacity (IEC); and 6.34 × 10⁻² S cm⁻¹ proton conductivity. The prepared PEM was classified as water enriched because of the presence of a high percentage of bound water content. A relatively high proton mobility (5.52 × 10⁻⁴ cm² s⁻¹ V⁻¹) across the PEM was attributed to a percolated network of ionic clusters (ions and water). Frictional data confirmed the reduction in frictional coefficient between the proton and membrane matrix at a high SSP content. The reported PEM, especially SPI/SSP-40, were assessed for their suitability for DMFC applications.
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