Sulfonated Polyether Ether Ketone / 3-(Trihydroxysilyl)-1-Propanesulfonic Acid Composite Membranes for Direct Methanol Fuel Cells
Fan Zhang, Sukhwan Yun, Javier Parrondo , Vijay Ramani
3-(trihydroxysilyl)-1-propanesulfonic acid (TPS) was used as a precursor to prepare sulfonated silica / sulfonated polyether ether ketone (SPEEK) composite membranes. Two batches of SPEEK with different ion exchange capacities (IEC) were prepared: SPEEK11 and SPEEK13, with IECs of 1.06±0.02mmolg-1 and 1.34±0.05mmolg-1, respectively. The ionic conductivity of the SPEEK membrane (at 60oC in DI water) increased by up to 15mS/cm upon incorporation of 15wt% TPS-derived sulfonated silica; the methanol permeability was at best slightly lowered (5-10%). A sharp reduction in ionic conductivity was observed at sulfonated silica loadings above 15-20wt%, as a consequence of changes in the ionic domains of the composite membrane. The morphological changes resulting from the introduction of sulfonated silica were investigated by small angle x-ray scattering (SAXS). The results were analyzed using two modeling approaches: a combined power-law and Teubner-Strey model, and a combined power-law and isolated scatterer model, suggesting the mean separation distances of composite membranes were 19.2, 20.2 and 21.1 Å for 10, 20 and 30wt% of TPS loading, respectively. The DMFC performances obtained (at 60oC using air and 3M methanol) using SPEEK11+5wt% TPS and SPEEK13+5wt% TPS composite membranes (187mA/cm2 and 240mA/cm2 at 0.4V) were better than the performance obtained with the pristine SPEEK membranes and a Nafion®1135 membrane, demonstrating that the performance of DMFC with SPEEK/sulfonated silica composite membranes was governed more by the proton conductivity rather than the methanol crossover.
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Sulfonated Polyether Ether Ketone / 3-(Trihydroxysilyl)-1-Propanesulfonic Acid Composite Membranes for Direct Methanol Fuel Cells, ACS Applied Materials and Interfaces, [online], https://doi.org/10.1149/2.0021409jes
(Accessed June 6, 2023)