A simple heat treatment to prepare covalently crosslinked membranes from sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) for application in fuel cells

Ionic transport properties improvement of a new cation-exchange membrane containing functionalized CNT as a clean technology for refining of saline-liquids

In the present research, a novel kind of homogeneous cation-exchange membranes were provided by solution casting technique via blending of sulfonated polyvinylchloride (SPVC) and sulfonated poly phenylene oxide (SPPO). The performance of the membranes was evaluated by membrane potential, areal resistance, transport number, ionic permeability, ion-exchange capacity, fixed ion concentration, energy consumption (EC), current efficiency, mechanical properties, membrane oxidative stability, water contact angle and water content tests. The microstructures of the membranes were investigated by scanning electron microscopy. Membrane with 70:30 (w/w) composition (SPPO: SPVC) exhibited suitable efficiency, mechanical strength and oxidative stability in comparison with other samples in this study. Also, amino groups have been successfully attached to the multi-walled carbon nanotubes (MWCNTs) structure and the modified MWCNTs were selected as filler additive. The results revealed that a series of membranes with improved transport properties, hydrophilicity and EC can be prepared with the polymeric matrix-containing aminated-MWCNTs.

Crosslinked Sulfonated Polyphenylsulfone-Vinylon (CSPPSU-vinylon) Membranes for PEM Fuel Cells from SPPSU and Polyvinyl Alcohol (PVA)

A crosslinked sulfonated polyphenylsulfone (CSPPSU) polymer and polyvinyl alcohol (PVA) were thermally crosslinked; then, a CSPPSU-vinylon membrane was synthesized using a formalization reaction. Its use as an electrolyte membrane for fuel cells was investigated. PVA was synthesized from polyvinyl acetate (PVAc), using a saponification reaction. The CSPPSU-vinylon membrane was synthesized by the addition of PVA (5 wt%, 10 wt%, 20 wt%), and its chemical, mechanical, conductivity, and fuel cell properties were studied. The conductivity of the CSPPSU-10vinylon membrane is higher than that of the CSPPSU membrane, and a conductivity of 66 mS/cm was obtained at 120 °C and 90% RH (relative humidity). From a fuel cell evaluation at 80 °C, the CSPPSU-10vinylon membrane has a higher current density than CSPPSU and Nafion212 membranes, in both high (100% RH) and low humidification (60% RH). By using a CSPPSU-vinylon membrane instead of a CSPPSU membrane, the conductivity and fuel cell performance improved.

Chemically Crosslinked Sulfonated Polyphenylsulfone (CSPPSU) Membranes for PEM Fuel Cells

Sulfonated polyphenylsulfone (SPPSU) with a high ion exchange capacity (IEC) was synthesized using commercially available polyphenylsulfone (PPSU), and a large-area (16 × 18 cm²) crosslinked sulfonated polyphenylsulfone (CSPPSU) membrane was prepared. In addition, we developed an activation process in which the membrane was treated with alkaline and acidic solutions to remove sulfur dioxide (SO₂), which forms as a byproduct during heat treatment. CSPPSU membranes obtained using this activation method had high thermal, mechanical and chemical stabilities. In I-V_{iR free} studies for fuel cell evaluation, high performances similar to those using Nafion were obtained. In addition, from the hydrogen (H₂) gas crossover characteristics, the durability is much better than that of a Nafion212 membrane. In the studies evaluating the long-term stabilities by using a constant current method, a stability of 4000 h was obtained for the first time. These results indicate that the CSPPSU membrane obtained by using our activation method is promising as a polymer electrolyte membrane.

Structurally modified aromatic sulfone polymer nanocomposites as polyelectrolyte membranes

A candid approach to analyze the prospects of organic–inorganic nanocomposites as polyelectrolytes has been presented in this communication. Structurally modified aromatic sulfone polymer, polysulfone, was successfully prepared through modification with trimethyl silyl chlorosulfonate, which was confirmed from Fourier transform infrared spectrographs. Different classes of nanofillers like layered silicates and inorganic oxides were reinforced in the modified macromolecular system using solvent casting technique. A comparative study was performed to evaluate the effectiveness of filled polyelectrolyte membranes in a direct methanol fuel cell operated at 60°C with 1.0 M methanol feed. Atomic force micrographs revealed the phase morphology, responsible for this behaviour. The variation in ion transfer behavior as a function of structural modification and filler composition was also conducted. Furthermore, supportive information for these characterizations were derived from morphological (x-ray diffractometry), thermal (thermogravimetric analysis), and liquid uptake studies.