Poly(ether ether ketone) (PEEK) was sulfonated at various degrees with sulfuric acid and dissolved in N,Ndimethylacetamide (DMAc). Montmorillonite (MMT) clay was mixed with this solution and solvent-casted on a glass plate. A Fourier transfer infrared (FTIR) experiment of sulfonated samples showed O-H vibration at 3490 cm -1 and SdO peaks at 1085 and 1100-1300 cm -1 . Thermogravimetry analyzer (TGA) experiments revealed thermal degradation above 240 °C. X-ray diffraction (XRD) confirmed almost zero crystallinity for sulfonated PEEK/MMT. When the degree of sulfonation was increased to 80%, ion-exchange capacity, water uptake, and proton conductivity were increased to almost 2.4 meq/g, 75%, and 0.06 S/cm, respectively. Methanol permeability was decreased to 5 × 10 -8 cm 2 /s by the addition of 10 wt % MMT. A sulfonated PEEK/MMT membrane with 62% of sulfonation and 1.0 wt % MMT loading showed membrane selectivity of approximately 8500 compare to 4500 of Nafion 117.
In the present study, a series of bioresource polyelectrolytes based on chitosan were synthesized and assessed for applicability in direct methanol fuel cells (DMFCs). A binary cross-linking agent (sulfosuccinic acid/glutaraldehyde) was used for the structural modification of chitosan and membranes comprising various amounts of sulfosuccinic acid (0, 8, 12, and 16 wt% SSA/wt chitosan) were prepared. It was found that by increasing the sulfonate groups' content up to 16 wt%, proton conductivity and methanol permeability properties reach the values of 0.0452 S cm S1 and 9.6 T 10 S7 cm 2 sec S1 , respectively. Based on the membrane selectivity evaluation and activation energy measurements of proton conduction, the optimum composition of cross-linking agent was determined. The optimum composition resulted in a relatively high proton conductivity of 0.0452 S cm S1 and a low methanol permeability of 9.6 T 10 S7 cm 2 sec S1 . Moreover, the optimum proton exchange membrane exhibited selectivity value of 47,100 in comparison with the corresponding value of 40,500 for Nafion 1 117. The fabricated membranes showed acceptable oxidative and hydrolytic stability. Furthermore, single cell DMFC performance test revealed a power density of 17 mW cm S2 at 30-C and 41 mW cm S2 at 60-C in a 2 M methanol feed. Hence, prepared proton-conducting bioresource ionomers could have promising potential in the field of green power generation as a low cost and biodegradable polyelectrolyte.
Here we show that the transport properties and electrochemical performance of polyelectrolyte membranes are improved through the dispersion of chitosan-wrapped carbon nanotubes, for direct methanol fuel cell applications. Methanol permeability is reduced via improving the interfacial interactions
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