Cross-Linked Sulfonated Poly(arylene ether sulfone) Membrane Using Polymeric Cross-Linkers for Polymer Electrolyte Membrane Fuel Cell Applications

Cross-linked membranes for polymer electrolyte membrane fuel cell application are prepared using highly sulfonated poly(arylene ether sulfone) (SPAES) and polymeric cross-linkers having different hydrophilicities by facile in-situ casting and heating processes. From the advantage of the cross-linked structures made with the use of polymeric cross-linkers, a stable membrane can be obtained even though the polymer matrix with a very high degree of sulfonation was used. In particular, hydrophilic cross-linker is found to be effective in improving physicochemical properties of the cross-linked membranes and at the same time showing reasonable proton conductivity. Accordingly, membrane electrode assembly made from the cross-linked membrane prepared by using hydrophilic polymeric cross-linker exhibits outstanding cell performance under high temperature and low relative humidity conditions (e.g., maximum power density of 176.4 mW cm^-2 at 120 °C and 40% RH).

Intercalated Poly (2-Acrylamido-2-methyl-1-propanesulfonic Acid) into Sulfonated Poly (1,4-Phenylene ether-ether-sulfone) Based Proton Exchange Membrane: Improved Ionic Conductivity

A series of hybrid proton exchange membranes were synthesized via in situ polymerization of poly (2-acrylamido-2-methyl-1-propanesulfonic acid) PMPS with sulfonated poly (1,4-phenylene ether-ether-sulfone) (SPEES). The insertion of poly (2-acrylamido-2-methyl-1-propanesulfonic acid) PMPS, between the rigid skeleton of SPEES plays a reinforcing role to enhance the ionic conductivity. The synthesized polymer was chemically characterized by fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance ¹H NMR spectroscopy to demonstrate the successful grafting of PMPS with the pendent polymer chain of SPEES. A variety of physicochemical properties were also investigated such as ion exchange capacity (IEC), proton conductivity, water uptake and swelling ratio to characterize the suitability of the formed polymer for various electrochemical applications. SP-PMPS-03, having the highest concentration of all PMPS, shows excellent proton conductivity of 0.089 S cm^-1 at 80 °C which is much higher than SPEES which is ~0.049 S cm^-1. Optimum water uptake and swelling ratio with high conductivity is mainly attributed to a less ordered arrangement polymer chain with high density of the functional group to facilitate ionic transport. The residual weight was 93.35, 92.44 and 89.56%, for SP-PMPS-01, 02 and 03, respectively, in tests with Fenton's reagent after 24 h. In support of all above properties a good chemical and thermal stability was also achieved by SP-PMPS-03, owing to the durability for electrochemical application.

Synergistic Effect of 2-Acrylamido-2-methyl-1-propanesulfonic Acid on the Enhanced Conductivity for Fuel Cell at Low Temperature

This present work focused on the aromatic polymer (poly (1,4-phenylene ether-ether-sulfone); SPEES) interconnected/ cross-linked with the aliphatic monomer (2-acrylamido-2-methyl-1-propanesulfonic; AMPS) with the sulfonic group to enhance the conductivity and make it flexible with aliphatic chain of AMPS. Surprisingly, it produced higher conductivity than that of other reported work after the chemical stability was measured. It allows optimizing the synthesis of polymer electrolyte membranes with tailor-made combinations of conductivity and stability. Membrane structure is characterized by ¹H NMR and FT-IR. Weight loss of the membrane in Fenton's reagent is not too high during the oxidative stability test. The thermal stability of the membrane is characterized by TGA and its morphology by SEM and SAXS. The prepared membranes improved proton conductivity up to 0.125 Scm^-1 which is much higher than that of Nafion N115 which is 0.059 Scm^-1. Therefore, the SPEES-AM membranes are adequate for fuel cell at 50 °C with reduced relative humidity (RH).

Poly(vinylidene fluoride-co-chlorotrifluoro ethylene) Nanohybrid Membrane for Fuel Cell

Through nanochannels are created in the polymer/hybrid films by irradiating swift heavy ions followed by selective chemical etching of the amorphous latent track caused by irradiation. The dimensions of the nanochannels are varied from 30 to 100 nm by either using small (lithium) and large (silver) size of swift heavy ions with high energy (80 MeV) or by embedding few percentage of two-dimensional nanoparticle in the polymer matrix. The side walls of the nanochannels are grafted with polystyrene using the free radicals created during irradiation. Polystyrene graft is functionalized by tagging sulfonate group in the benzene ring of polystyrene to make the nanochannels conducting and hydrophilic. The proof of grafting and functionalization is shown through various spectroscopic techniques. The relaxation behavior and thermal stability of graft polymer within the nanochannel are shown through different thermal measurements. Nanoclay in nanohybrid nucleates the piezoelectric phase in the polymer matrix whose extent is further increased in grafted and functionalized specimen. Functionalized nanochannels exclusively facilitate proton conducting, whereas the remaining part of the film is electroactive, making it as a smart membrane. Greater water uptake, ion exchange capacity (IEC), high activation energy (8.3 × 103 J mol-1), and high proton conduction (3.5 S m-1) make these functionalized nanohybrid film a superior membrane. Membrane electrode assembly has been made to check the suitability of these membranes for fuel cell application. Open circuit voltage and potential are significantly high for nanohybrid membrane (0.6 V) as compared to pure polymer (0.53 V). Direct methanol fuel cell testing using the membrane assembly exhibit a considerable high power density of ∼400 W m-2, making these developed membranes suitable for fuel cell application and providing the ability to replace standard membrane like Nafion, as the methanol permeability is low, thus raising the higher selectivity parameter of the nanohybrid membrane.

Silane Cross-Linked Sulfonted Poly(Ether Ketone/Ether Benzimidazole)s for Fuel Cell Applications

γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH-560) was incorporated in various proportions into side-chain-type sulfonated poly(ether ketone/ether benzimidazole) (SPEKEBI) as a crosslinker, to make membranes with high ion exchange capacities and excellent performance for direct methanol fuel cells (DMFCs). Systematical measurements including Fourier transform infrared (FT-IR), scanning electron microscopy-energy-dispersive and X-ray photoelectron spectroscopy (XPS) proved the complete disappearance of epoxy groups in KH-560 and the existence of Si in the membranes. The resulting membranes showed increased mechanical strength and thermal stability compared to the unmodified sulfonated poly(ether ketone/ether benzimidazole) membrane in appropriate doping amount. Meanwhile, the methanol permeability has decreased, leading to the increase of relative selectivities of SPEKEBI-x-SiO₂ membranes. Furthermore, the H₂/O₂ cell performance of SPEKEBI-2.5-SiO₂ membrane showed a much higher peak power density compared with the pure SPEKEBI memrbrane.

Hybrid composite membranes of chitosan/sulfonated polyaniline/silica as polymer electrolyte membrane for fuel cells

A series of novel ionic cross-linked chitosan (CS) based hybrid nanocomposites were prepared by using polyaniline/nano silica (PAni/SiO₂) as inorganic filler and sulfuric acid as an ionic cross-linking agent. The CS-PAni/SiO₂ nanocomposites show enhanced mechanical properties and improved oxidative stabilities. These nanocomposites can be effectively used as environmental friendly proton exchange membranes. Incorporation of PAni/SiO₂ into CS matrix enhances water uptake and facilitates the phase separation which enables the formation of hydrophilic domains and improves the proton transport. Moreover, the doped polyaniline also provides some additional pathways for proton conduction. The membrane containing 3wt% loading of PAni/SiO₂ in chitosan (CS-PAni/SiO₂-3) exhibits high proton conductivity at 80°C (8.39×10^-3Scm^-1) in fully hydrated state due to its excellent water retention properties. Moreover, methanol permeability of the ionic cross-linked CS-PAni/SiO₂ nanocomposite membranes significantly reduces with the addition of PAni/SiO₂ nano particles. The CS-PAni/SiO₂-3 composite membrane displays the best overall performance as a polymer electrolyte membrane.

Fabrication and evaluation of polymeric membranes for blood dialysis treatments using functionalized MWCNT based nanocomposite and sulphonated-PES

The use of polyethersulfone based membranes for dialysis therapy is increasing, but the poor bio-compatibility of the PES membrane can raise severe blood reactions affecting the rate of morbidity and mortality of hemodialysis (HD) patients.

Enhanced performance of poly(ether sulfone) based composite proton exchange membranes with sulfonated polymer brush functionalized graphene oxide

Novel poly(ether sulfone) based composite proton exchange membranes with enhanced performance were prepared by incorporating sulfonated polymer brush functionalized GO.

Sulfonated polyimide/acid-functionalized graphene oxide composite polymer electrolyte membranes with improved proton conductivity and water-retention properties

Sulfonated polyimide (SPI)/sulfonated propylsilane graphene oxide (SPSGO) was assessed to be a promising candidate for polymer electrolyte membranes (PEMs). Incorporation of multifunctionalized (-SO3H and -COOH) SPSGO in SPI matrix improved proton conductivity and thermal, mechanical, and chemical stabilities along with bound water content responsible for slow dehydration of the membrane matrix. The reported SPSGO/SPI composite PEM was designed to promote internal self-humidification, responsible for water-retention properties, and to promote proton conduction, due to the presence of different acidic functional groups. Strong hydrogen bonding between multifunctional groups thus led to the presence of interconnected hydrophobic graphene sheets and organic polymer chains, which provides hydrophobic-hydrophilic phase separation and suitable architecture of proton-conducting channels. In single-cell direct methanol fuel cell tests, SPI/SPSGO-8 exhibited 75.06 mW·cm(-2) maximum power density (in comparison with commercial Nafion 117 membrane, 62.40 mW·cm(-2)) under 2 M methanol fuel at 70 °C.

A novel fuel cell membrane with high efficiency

A novel polymer containing an azo based ionic diol has been successfully fabricated as an electrolyte membrane to yield a good fuel cell performance in the whole range of current density.

Ion pair reinforced semi-interpenetrating polymer network for direct methanol fuel cell applications

This paper describes the synthesis of ion-pair-reinforced semi-interpenetrating polymer networks (SIPNs) as proton exchange membranes (PEMs) for the direct methanol fuel cells (DMFCs). Specifically, sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), a linear polymer proton source, was immobilized in a brominated PPO (BPPO) network covalently cross-linked by ethylenediamine (EDA). The immobilization of SPPO in the SIPN network was accomplished not only by the usual means of mechanical interlocking but also by ion pair formation between the sulfonic acid groups of SPPO and the amine moieties formed during the cross-linking reaction of BPPO with EDA. Through the ion pair interactions, the immobilization of SPPO polymer in the BPPO network was made more effective, resulting in a greater uniformity of sulfonic acid cluster distribution in the membrane. The hydrophilic amine-containing cross-links also compensated for some of the decrease in proton conductivity caused by ion pair formation. The SIPN membranes prepared as such showed good proton conductivity, low methanol permeability, good mechanical properties, and dimensional stability. Consequently, the PPO based SIPN membranes were able to deliver a higher maximum power density than Nafion, demonstrating the potential of the SIPN structure for PEM designs.