•Alcohol solvent for hydrocarbon polymer electrolyte (SPPSU).•Improvement of a stability of the SPPSU membrane using annealing processing.•High proton conductivity for PEMFCs.Sulfonated polyphenylsulfone (SPPSU) membranes were prepared using alcohol solvents such as isopropanol and 1-propanol in combination with a highly sulfonated PPSU polymer. A covalently crosslinked membrane was obtained after annealing at 180 °C without a crosslinker. The membrane was stable in water, and the thermal stability was higher than that of a synthesized SPPSU polymer. This higher stability was because of the crosslinking effect through the sulfonyl and/or phenyl groups of SPPSU. A high conductivity of 0.1 S/cm and power density of 471 mW/cm2 were obtained at 80 °C and relative humidity (RH) 100%.

Highly sulfonated polyethersulfone (SPES; Ione exchange capacity = 3.2 meq/g) and polyphenylsulfone (SPPSU; ion exchange capacity = 3.2 meq/g) were synthesized. To get high thermal and chemical stability, a blend membrane was prepared by the composite of SPES and SPPSU. The SPES-SPPSU blend membrane after the annealing treatment at 180 °C was stable in water and other organic solvents, and the thermal stability was also more increased than that of pristine SPES and SPPSU polymers due to the crosslinking formation among SPES and SPPSU. The maximum conductivity of 0.12 S/cm was obtained at the temperature of 140 °C and RH 90%.Highlights► Highly sulfonated polyethersulfone and polyphenylsulfone membrane. ► Crosslinked SPES-SPPSU membrane by annealing treatment. ► High proton conductivity for high temperature PEMFCs.

The properties of sulfonated poly(ether ether ketone) (SPEEK) were investigated by various solvents such as N-methly-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and dimethylformamide (DMF). The SPEEK membranes were activated by the solution of 1 M H2SO4 to remove the remaining solvents in the membranes. The properties of proton conductivity and cell performance of the membranes after activated treatment were improved compared to those of before activated treatment. Especially, the proton conductivity and cell performance of the SPEEK membrane using NMP as a solvent was the equal to that of the Nafion 117 membrane. We suggest that the selection of a casting solvent and membrane activation treatment for removing of the remaining solvent in the membrane can be a very important factor to get a high performance membrane.Highlights► Solvent casting effects of SPEEK membrane. ► Removing of solvents (NMP, DMAc, DMF, and DMSO) remaining into the membranes. ► Proton conductivity and cell performance of the as-cast and activated membranes.

Anhydrous nafion-benzimidazole (bz) blend membranes were prepared by room temperature and autoclave solution processing. The physico-chemical properties of anhydrous nafion-bz blend membranes using different solution processing were investigated by TG-DTA, dynamic elastic modulus, XRD, SAXS, and proton conductivity. The nafion-bz blend membrane using autoclave solution processing improved the properties such as a flexibility, density, homogeneity and dynamic elastic modulus, while the crystalline in a macroscopic crystal structure and proton conductivity was nearly the same.

New organic–inorganic hybrid crystalline electrolytes comprised of 12-phosphotungstic acid (PWA) and the ionic liquid [1-butyl-3-methylimidazole][bis-(fluoromethanesulfonyl)amide] ([BMIM][TFSI]) with high thermal stability and high ion conductivity at high temperatures were obtained. In the new hybrids, there was a strong interaction between [BMIM]+ of the ionic liquid and PWA. The hybrids were very stable up to about 400 °C and showed a high ion jump during heating and cooling processes. Based on results from TG–DTA, DSC, and NMR spectroscopy, the ion jump was due to melting and solidification of the hybrid. The structures of powder and single-crystal samples of the hybrids were also studied. The chemical formula of the hybrid in the single crystal was determined to be PW13C32H56O54N8S0.16F0.26. This is nearly the same as those determined from the powder samples. By analyzing single-crystal X-ray diffraction (XRD) data, the hybrid was determined to crystallize in the space group Pca21 with the lattice constants a = 18.316(3), b = 18.327(3), and c = 16.657(3) Å. The powder XRD data of the hybrid were assigned.

Ionogel electrolytes at medium temperatures were prepared by composite of ionic liquid [1-butyl-3-methylimidazole][bis-(fluoromethanesulfonyl) amide] ([BMIM][TFSI]) with the proton-conducting inorganic solid acid CsHSO4. The incorporation of only 10 wt.% of the ionic liquid into the solid acids drastically increased the conductivity of solid acids over a wide temperature range. The ionogel electrolytes contained up to 40 wt.% of the ionic liquid within their inorganic CsHSO4 networks and had an ion conductivity of 2 × 10− 2 S/cm.

A lamella-structured inorganic–organic zirconium–monododecyl phosphate crystalline hybrid was investigated as an anhydrous proton conductor. Inorganic zirconium ions were coordinated by OH groups of a phosphate moiety from organic monododecyl phosphate. The inorganic–organic zirconium–monododecyl phosphate hybrid showed a lamella structure with crystalline ZrP, and the thermal stability increased up to 230 °C. A maximum proton conductivity of 2 × 10−3 S cm−1 was obtained at 150 °C under anhydrous conditions. The high proton conductivity under high temperature and anhydrous conditions could be explained by considering the interaction between Zr ions and the phosphate group, and the phosphate concentration in the lamella-structured inorganic–organic zirconium–monododecyl phosphate hybrid.

In this study, we synthesized a molecular hybrid conductor electrolyte using PWA ([H3PW12O40·nH2O]) and [1-butyl-3-methylimidazole][bis-(fluoromethanesulfonyl) amide] ([BMIM][TFSI]) ionic liquid. The [BMIM][TFSI] ionic liquid can interact with the strongly acidic PWA. The hybrids were hydrophilic, and included some water molecules in the structure of the hybrids. The water molecules remained up to 80 °C, contributing to improve conductivity under an anhydrous N2 atmosphere. The conductivity of PWA-[BMIM][TFSI] hybrid under anhydrous conditions increased from 10−4 S/cm to 0.04 S/cm at 60 °C. The conductivity of the hybrids at each temperature was higher than that of pure PWA and [BMIM][TFSI] under anhydrous condition. It can be due to the protonic carriers.

Proton exchange membranes with chemically tolerant organically modified zirconia are prepared by inorganic–organic self-assemble sol–gel process. The monomers were covalently bonded at the zirconia interface to form macromolecular inorganic–organic networks. The modified inorganic–organic hybrid membranes showed high flexibility, chemical tolerance, mechanical property and thermal stability up to 325 °C. For the proton exchange membrane, the organically modified hybrids were put into the condition of room temperature or boiled in 85% H3PO4 at 150 °C. The proton conductivity of the ion exchange membranes was investigated.