Synthesis and Characterization of Novel Anion Exchange Membranes Based on Semi-Interpenetrating Networks of Functionalized Polysulfone: Effect of Ionic Crosslinking

Anion Exchange Membrane Based on BPPO/PECH with Net Structure for Acid Recovery via Diffusion Dialysis

In order to improve the performance of the anion exchange membrane (AEM) used in acid recovery from industrial wastewater, this study adopted a new strategy in which brominated poly (2,6-dimethyl-1,4-phenyleneoxide) (BPPO) and polyepichlorohydrin (PECH) were used as the polymer backbone of the prepared membrane. The new anion exchange membrane with a net structure was formed by quaternizing BPPO/PECH with N,N,N,N-tetramethyl-1,6-hexanediamine (TMHD). The application performance and physicochemical property of the membrane were adjusted by changing the content of PECH. The experimental study found that the prepared anion exchange membrane had good mechanical performance, thermostability, acid resistance and an appropriate water absorption and expansion ratio. The acid dialysis coefficient (U_H⁺) of anion exchange membranes with different contents of PECH and BPPO was 0.0173-0.0262 m/h at 25 °C. The separation factors (S) of the anion exchange membranes were 24.6 to 27.0 at 25 °C. Compared with the commercial BPPO membrane (DF-120B), the prepared membrane had higher values of U_H⁺ and S in this paper. In conclusion, this work indicated that the prepared BPPO/PECH anion exchange membrane had the potential for acid recovery using the DD method.

Influence of sulfonated SBA - 15 on fuel cell performance of sulfonated polysulfone electrolyte membranes

The prepared mesoporous SBA-15 (Santa Barbara Amorphous-15) was sulfonated and used as filler for the preparation of sulfonated polysulfone based composite electrolyte membranes. The SBA-15 and polysulfone were sulfonated using 3-mercaptopropyl trimethoxysilane and trimethylsilyl chlorosulfonate, respectively. The different weight percentages (1, 3, and 5 wt%) of sulfonated SBA-15 (SSBA-15) were used to prepare composite electrolyte membranes. Water uptake, ion exchange capacity, swelling ratio and proton conductivity of the composite membranes were studied for assessing the suitability of the electrolyte membranes for use in fuel cells. Characterization techniques such as FT-IR, XRD, SEM, TEM and Brunauer–Emmett– Teller were used to study the physico-chemical properties of the electrolyte membranes. TEM and BET analysis showed that SBA -15 retained its mesoporous structure even after sulfonation process. The prepared membranes were then tested in an in-house built single-cell fuel cell using hydrogen as fuel and oxygen as the oxidant. The fuel cell study showed that the presence of Sulfonated SBA-15 in the polymer matrix provided additional ion exchange sites and retained water for proton transfer which resulted in higher power density of 815 mW/cm2 with SPSU + 3% SSBA-15 membrane as compared with Nafion 117®.

Design Strategies for Alkaline Exchange Membrane-Electrode Assemblies: Optimization for Fuel Cells and Electrolyzers

Production of hydrocarbon-based, alkaline exchange, membrane-electrode assemblies (MEA's) for fuel cells and electrolyzers is examined via catalyst-coated membrane (CCM) and gas-diffusion electrode (GDE) fabrication routes. The inability effectively to hot-press hydrocarbon-based ion-exchange polymers (ionomers) risks performance limitations due to poor interfacial contact, especially between GDE and membrane. The addition of an ionomeric interlayer is shown greatly to improve the intimacy of contact between GDE and membrane, as determined by ex situ through-plane MEA impedance measurements, indicated by a strong decrease in the frequency of the high-frequency zero phase angle of the complex impedance, and confirmed in situ with device performance tests. The best interfacial contact is achieved with CCM's, with the contact impedance decreasing, and device performance increasing, in the order GDE >> GDE+Interlayer > CCM. The GDE+interlayer fabrication approach is further examined with respect to hydrogen crossover and alkaline membrane electrolyzer cell performance. An interlayer strongly reduces the rate of hydrogen crossover without strongly decreasing electrolyzer performance, while crosslinking the ionomeric layer further reduces the crossover rate though also limiting device performance. The approach can be applied and built upon to improve the design and production of alkaline, and more generally, hydrocarbon-based MEA's and exchange membrane devices.

Dimethylimidazolium-Functionalized Polybenzimidazole and Its Organic-Inorganic Hybrid Membranes for Anion Exchange Membrane Fuel Cells

A quaternized polybenzimidazole (PBI) membrane was synthesized by grafting a dimethylimidazolium end-capped side chain onto PBI. The organic-inorganic hybrid membrane of the quaternized PBI was prepared via a silane-induced crosslinking process with triethoxysilylpropyl dimethylimidazolium chloride. The chemical structure and membrane morphology were characterized using NMR, FTIR, TGA, SEM, EDX, AFM, SAXS, and XPS techniques. Compared with the pristine membrane of dimethylimidazolium-functionalized PBI, its hybrid membrane exhibited a lower swelling ratio, higher mechanical strength, and better oxidative stability. However, the morphology of hydrophilic/hydrophobic phase separation, which facilitates the ion transport along hydrophilic channels, only successfully developed in the pristine membrane. As a result, the hydroxide conductivity of the pristine membrane (5.02 × 10-2 S cm-1 at 80 °C) was measured higher than that of the hybrid membrane (2.22 × 10-2 S cm-1 at 80 °C). The hydroxide conductivity and tensile results suggested that both membranes had good alkaline stability in 2M KOH solution at 80 °C. Furthermore, the maximum power densities of the pristine and hybrid membranes of dimethylimidazolium-functionalized PBI reached 241 mW cm-2 and 152 mW cm-2 at 60 °C, respectively. The fuel cell performance result demonstrates that these two membranes are promising as AEMs for fuel cell applications.