SPEEK-based proton exchange membranes modified with MOF-encapsulated ionic liquid

Abstract

1-butyl-3-methylimidazolium sulfate (BMI.HSO4), 1-butylimidazole sulfate (BImH.HSO4) and 3-triethylammonium hydrogen sulfate (TEA-PS.HSO4) ionic liquids were encapsulated in UiO-66 (Zr-MOF) framework. These materials were incorporated into sulfonated poly(ether ether ketone) (SPEEK) membranes in different concentrations of ionic liquid. The influence of ionic liquid concentration encapsulated in Zr-MOF was evaluated through the morphology and thermal and chemical stability of the modified membranes. The incorporation of 7.5 wt.% Zr-MOF in SPEEK produced membranes with high proton conductivity, making this the best mass ratio for the incorporation of the ionic liquids. Contact angle and swelling analysis indicate that the presence of these ionic liquids provides stability to the membrane, preventing it from absorbing high amounts of water. Mass ratios of 2.5 and 5.0 wt.% of encapsulated ILs in Zr-MOF were also used. Proton conductivity results show that a higher concentration of ionic liquid generates agglomerates, limiting proton mobility in the membranes. Among the three ionic liquids tested, TEA-PS.HSO4 presents the best proton conductivity values, between 92 and 140 mS cm-1. These results indicate a possible application in proton exchange membrane fuel cells (PEMFCs).

Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges

“…These composite membranes showed a significant increase in their proton conductivity over the recast SPEEK, reaching values up to 0.27 S/cm at 70 °C and 95% RH [ 125 ]. Ionic liquids can also be encapsulated into the UiO-66 cavities, creating SPEEK composite membranes with conductivities up to 0.14 S/cm at 80 °C and 60% RH [ 126 ]. Although other different MOFs have been used as filler in SPEEK membranes, the conductivities were far from those achieved with the widely used MIL-101 and UiO-66 [ 127 , 128 ].…”

Investigation on the sulfonated poly(ether ether ketone)/poly(amide‐imide)/barium cerate‐based nanocomposite membrane for proton exchange membrane fuel cells

“…The production of free radicals hydroxyl (HO ● ) and hydroperoxy (HOO ● ) gives a significant impact on cell performance and membrane deterioration in electrolyte sections 33 . The clean SPEEK loses more weight than another membrane owing to more free availability of HSO 3 groups in the matrices.…”

“…The production of free radicals hydroxyl (HO • ) and hydroperoxy (HOO • ) gives a significant impact on cell performance and membrane deterioration in electrolyte sections. 33 The clean SPEEK loses more weight than another membrane owing to more free availability of HSO 3 groups in the matrices. The BaCeO 3 nanoparticle interacting with blended membrane (SPEEK/PAI) makes the acid-acid and acid-base ionic cross-linking that preserves hydroxyl from deterioration circumstance.…”

Novel Polymeric Composite TPPS/s-PEEK Membranes for Low Relative Humidity PEFC

“…In order to maintain an adequate proton conductivity and preserve the mechanical properties, under low RH conditions, hygroscopic and/or proton conductor fillers are introduced into the membrane, as well as blending with other polymers, with the aim of maintaining the appropriate amount of water for proton conduction [11][12][13]. The fillers generally used for this purpose are composed of ceramic oxides or functionalized oxides, polymers with specific functional groups and organic compounds [14][15][16][17][18][19][20][21][22][23][24]. In this framework, the insertion of compounds or polymers containing nitrogenous groups, due to the ability of specific interactions/bonding with the sulfonic groups, is considered fruitful to reduce the swelling effect at high temperature and to improve the proton conductivity [25][26][27][28][29][30].…”