Sulfonated polysulfone as promising membranes for polymer electrolyte fuel cells

Abstract

A new, milder sulfonation process was used to produce ion-exchange polymers from a commercial polysulfone (PSU). Membranes obtained from the sulfonated polysulfone are potential substitutes for perfluorosulfonic acid membranes used now in polymer electrolyte fuel cells. Sulfonation levels from 20 to 50% were easily achieved by varying the content of the sulfonating agent and the reaction time. Ion-exchange capacities from 0.5 to 1.2 mmol SO 3 H/g polymer were found via elemental analysis and titration. Proton conductivities between 10 Ϫ6 and 10 Ϫ2 S cm Ϫ1 were measured at room temperature. An increase in intrinsic viscosity with increasing sulfonation degree confirms that the sulfonation process helps to preserve the polymer chain from degradation. Thermal analysis of the sulfonated polysulfone (SPSU) samples reveals higher glass transition temperatures and lower decomposition temperatures with respect to the unsulfonated sample (PSU). Amorphous structures for both PSU and SPSU membranes were detected by X-ray diffraction analysis and differential scanning calorimetry. Preliminary tests in fuel cells have shown encouraging results in terms of cell performance.

Acid–base blend membranes based on 2-amino-benzimidazole and sulfonated poly(ether ether ketone) for direct methanol fuel cells

“…Several non-fluorinated polymeric materials have been investigated as replacements for Nafion due to low cost and ease of synthesis [5][6][7][8][9][10][11][12], but they are generally based on free sulfonic acid groups and experience severe dimensional swelling in DMFC at high degree of sulfonation, resulting in mechanical instability problems [1,12,13]. Cross-linked ionomers have been pursued to overcome this problem, but they usually lead to a sacrifice in fuel cell performance and microphase-separation is easy to occur in such blends due to different, incompatible acidic (aromatic) and basic (polybenzimidazole) polymer structures [14,15].…”

Organic/Inorganic Nanocomposite Membranes Development for Low Temperature Fuel Cell Applications

“…In the other procedure, trimethylsilyl chlorosulfonate was used as the sulfonating agent (Baradie et al, 1998). Lufrano et al (2000Lufrano et al ( ,2001 prepared SPSU via trimethylsilyl chlorosulfonate with different degrees of sulfonation (DS). Different membranes with sulfonation degree from 23% to 53% (Lufrano et al, 2000) on the one hand and 49%, 61% and 77% on the other hand were prepared.…”

“…Lufrano et al (2000Lufrano et al ( ,2001 prepared SPSU via trimethylsilyl chlorosulfonate with different degrees of sulfonation (DS). Different membranes with sulfonation degree from 23% to 53% (Lufrano et al, 2000) on the one hand and 49%, 61% and 77% on the other hand were prepared. With a 61% sulfonation degree a proton conductivity for SPSU of 2.7  10 -2 S/cm at 25°C was reported ).…”

Towards Extrusion of Ionomers to Process Fuel Cell Membranes

“…The reaction was performed in anhydrous conditions under an Argon flow, which allowed the gaseous HCl, generated by the electrophilic substitution, to be removed promptly. Trimethylsilylchlorosulfonate (TMSClS) was chosen as the sulfonating reagent because it is among the less aggressive reagents [3,13,14,20]. Moreover, due to the formation of a trimethylsilyl sulfonic ester rather than a sulfonic acid, the hydrophobic character of PSF was retained and prevented any partial precipitation during the reaction.…”