Broadband dielectric spectroscopy of Nafion‐117, sulfonated polysulfone (sPSF) and sulfonated polyether ketone (sPEK) membranes

Abstract

Nafion®-117, sulfonated polysulfone (sPSF) and sulfonated polyetherketone (sPEK) are characterized using broadband dielectric spectroscopy in the frequency range of 10 MHz–100 mHz. Overall, there are 4-5 relaxation processes in these sulfonated membranes and a comparison of their spectral features allows assigning the relaxation processes. At an optimum amplitude of ~100 mVrms, all the relaxations are clearly defined as the electrode polarization is minimized. At low temperatures (-130°C), these membranes show a broad relaxation peak in the mid-frequency region, which quickly shifts towards the high-frequency region as the temperature is increased to -90°C. This peak is observed in proton exchange membranes for the first time due to the use of low ac amplitude, and it is assigned to the relaxation of the confined water in the micro-pores. With all the membranes, the peak associated with -SO3H group relaxation is observed in the same frequency range at a temperature of ~-80°C

Polyaryletherketone in energy conversion and storage devices – a highly tailorable material with versatile properties

“…As observed in one of our previous reports (Fig. 4), the XRD patterns of the membrane formed through phase inversion and solvent drying clearly show a lack of prominent peaks with the membrane prepared by the former method due to insufficient time for crystallization 7 . The reduced crystallization results in lesser stacking of the polymer chains and formation of spherulites which in turn favours the formation of more channels for ion conduction.…”

“…and the solvent used. The most commonly used solvents for PAEKs are N ‐methyl‐2‐pyrrolidone, N , N ′‐dimethylacetamide, N , N ′‐dimethylformamide (DMF), dimethylsulfoxide, sulfuric acid (H 2 SO 4 ) and p ‐chlorophenol 7,11,28,29 . The variation in properties of the membranes cast through different solvents is attributed to the solvent interaction with the –SO 3 H group 28 .…”

“…In the phase inversion technique, the polymer solution is usually more concentrated and it is spread on a glass substrate using a doctor blade to obtain uniform thickness of the membrane. Depending on the morphology required, it may be exposed to air for a certain duration before immersing it in water or an ethanol bath 7,23 . The sudden replacement of solvent by water results in a porous structure of the membrane and the porosity can be controlled by varying the polymer concentration and air drying time.…”

“…Therefore, in the pursuit of replacing the commercial Nafion membrane, considerable research has been expended on developing alternative materials for polymer electrolyte membrane fuel cells (PEMFCs). The most commonly used polymers are sulfonated polysulfone (sPS), polyvinylidene fluoride, sulfonated polyetheretherketone (sPEEK), sulfonated polystyrene, polybenzimidazoles (PBI/ABPBI), sulfonated polyimide etc 6–12 . The comparatively low cost of PAEK membranes and high temperature stability makes them suitable candidates as alternative membrane material.…”

Electrochemical Impedance Spectroscopic Investigation of Vanadium Redox Flow Battery

“…Afterwards, it was boiled in DI water for 30 min to remove traces of acid from the surface of the membrane. 56 A pre-treated carbon felt and Ag/AgCl reference electrodes were kept in the VO 2+ electrolyte. A platinum coil (∼5 cm 2 ) was used as a counter electrode in the chamber containing 3 M H 2 SO 4 solution.…”