Behavior of sulfonated poly(ether ether ketone) in ethanol–water systems

Abstract

The behavior of sulfonated poly(ether ether ketone) (sPEEK) membranes in ethanol-water systems was studied for possible application in direct ethanol fuel cells (DEFCs). Polymer membranes with different degrees of sulfonation were tested by means of uptake, swelling, and ethanol transport with dynamic measurements (liquid-liquid and liquid-gas systems). Ethanol permeability was determined in an liquid-liquid diffusion cell. For membranes with an ion-exchange capacity (IEC) between 1.15 and 1.75 mmol/g, the ethanol permeability varied between 5 x 10(-8) and 1 x 10(-6) cm(2)/s, being dependent on the measuring temperature. Ethanol and water transport in liquid-gas systems was tested with pervaporation as a function of IEC and temperature. Higher IEC accounted for higher fluxes and lower water/ethanol selectivity. The temperature had a large effect on the fluxes, but the selectivity remained constant. Further-more, the membranes were characterized with proton conductivity measurements. The proton diffusion coefficient was calculated, and a transition in the proton transfer mechanism was found at a water number of 12. Membranes with high IEC (>1.6 mmol/g) exhibited larger proton diffusion coefficients in ethanol-water systems than in water systems. The membrane with the lowest IEC exhibited the best proton transport to ethanol permeability selectivity. The use of sPEEK membranes in DEFC systems depends on possible modifications to stabilize the membranes in the higher conductive region rather than on modifications to increase the proton conductivity in the stable region

Graphene Membranes: Transport Properties and Energy Applications

“…Because membranes with high sulfonation tend to be very hydrophilic, this causes major swelling, poor mechanical properties, and fuel permeability, causing a disadvantage [61] However, graphene membranes such as GO with sulfonic acid groups paired with Nafion® improves the compatibility. Ultimately, this indicates that the incorporation of graphene into PEMs optimize the overall performance [77]. Recently, GN-based membranes have also been used successfully as anion exchange membranes (AEMs).…”

Sulfonated dendrimer‐ and hyperbranched polyglycerol‐PBIOO® blend membranes for fuel cells

“…PBI is a commercially available basic polymer that shows excellent chemical, thermal, and mechanical stability, although it must be functionalized and/or doped with an acid to enhance the hydrophilicity and proton conductivity in order to be used as a PEM material . In general, the proton conductivity of polymers is improved by a high degree of sulfonation but this leads to high swelling of the membrane, which in turn leads to a loss of mechanical strength and an increase in the methanol permeability . The blending of acidic and basic polymers is one of the approaches used to overcome the problems related to swelling .…”

“…[8][9][10] In general, the proton conductivity of polymers is improved by a high degree of sulfonation but this leads to high swelling of the membrane, which in turn leads to a loss of mechanical strength and an increase in the methanol permeability. 11 The blending of acidic and basic polymers is one of the approaches used to overcome the problems related to swelling. 12 The physical cross-linking introduced by the ionic interactions between acidic and basic groups provides membranes with improved flexibility and mechanical properties in the wet state compared with non-cross-linked or covalently cross-linked membranes.…”

Impact of Mesoporous and Microporous Materials on Performance of Nafion and SPEEK Polymer Electrolytes: A Comparative Study in DEFCs

“…As far as non-fluoro polymeric electrolytes are concerned, sulfonated polyether ether ketone (SPEEK) based inorganic composite materials are widely studied in the literature [16]. Roelofs et al [17,18] have studied SPEEK membranes and its composites with addition of various silica materials and found lower ethanol permeability and good electrochemical selectivity in DEFCs. Tan et al [19] explored nanocomposite membranes based on heteropolyacid (HPA) sealed silica matrix with SPEEK/PES blend membranes showing improved proton conductivity and lower ethanol sorption.…”