Organic-inorganic Composite Membranes Research Articles

Evaluation of the Electrospun Inorganic/Organic Composite Membrane for High Temperature PEMFC

Abstrast High temperature fuel cell has been highlighted for its use in the wide range of the applications because of its simplified system due to easier integration and high energy efficiency.[1-2] There are several fascinating reasons for operating PEMFC at high temperature and low related humidity such as electrochemical kinetics, CO poisoning of Pt/C catalyst and water management. Also, the lifetime targets (5000 h stated objective by DOE) must be achieved while the costs of the fuel cell systems must be reduced concurrently.[1] In order to ameliorate the durability and lifetime of PEMFCs, a better analyzing of failure tools and corresponding mitigation methods are urgently required.[2] In the development of membranes that can effectively operate under higher temperature and lower humidity conditions, researchers have suggested organic-inorganic composite membranes with inorganic particulate additives.[3] Some of the composite membranes with particulate additives have shown improved fuel cell performance at high temperature and low humidity because of improved hydroscopic and thermal stability. Nevertheless, in practice, composite film casting by solvent evaporation or extrusion is often challenging due to particle agglutination. Recently, ceramic nanofibers have been prepared via electrospinning.[4] The uniformly dispersed 3-dimensional foam-like inorganic nanofibrous web completely resolved the agglomeration issue of particulate additives. The aspect ratio of the fibers was extremely high thereby providing additional mechanical strength to the composite membrane that could not be achieved by particulate additives.In this study, we prepared inorganic nanofibrous web supported polymer electrolyte membrane to increase operating temperature of the pristine polymer electrolyte membrane. Accelerated life-time tests (ALT) by changing the voltage sweep were developed to have better understanding of the degradation mechanisms in the fuel cell system. Further, factors of degradation were studied by conducting the electrochemical methods and characterizations.Gravimetric swelling by water of the Aquivion-impregnated inorganic nanofibrous webs as a membrane was higher than Aquivion cast film (32.8% vs. 17.5%) but more importantly, no length change in x- and y-axis was observed in wet state due to the presence of rigid inorganic nanofibrous webs uniformly distributed in the membrane. Therefore, no areal expansion of membrane is expected in the actual fuel cell test that would be beneficial to mechanically stable operation. A single cell with Aquivion/phosphate modified inorganic nanofiber composite membrane showed the best performance at partially humidified condition of 120 °C / 40% RH. It was expected that the higher water retention of the Aquivion/ phosphate modified inorganic nanofiber composite membrane played a beneficial role that the phosphate functionality enhanced proton conductivity by enhancing proton transfer through the Grotthus mechanism at higher temperature and the lower humidity conditions.

Characterization of Ion Exchange Membrane Based on Hydrocarbon Based Polymer and Functional Additives

A sol-gel method and an in situ method were used to synthesize organic-inorganic composite membranes based on poly(arylene ether sulfone) (SPAES), phosphotungstic acid (PWA) containing sulfonic acid and amine groups. HPA is generally water soluble and causing a deterioration of cell performance. To solve this problem, PWA particles were functionalized with various silane compounds to enhance proton conductivity and to possess insoluble property in water. This study compares the performance of polymer electrolyte membrane fuel cells with different preparation methods for the membrane and composite PWA-silica-SO3H particles. The optimum composition of PWA-silica-SO3H and effect of amine groups in SPAES composite membrane are determined on the basis of the mechanical properties, the behavior of water in the membrane, and the level of proton conductivity. The mechanical properties of the composite membrane prepared by sol-gel method were improved with the introduction of PWA-silica-SO3H particles. Also, the sol-gel composite membrane containing amine groups has higher levels of proton conductivity than the other composite membranes. An increase in the silica content of the PWA-silica sol-gel particles increases the ion conductivity because the inorganic component and the incorporation of PWA lead to a high concentration of functional.

PEMWE를 위한 Cs치환에 따른 공유가교 SPEEK/Cs(x)-TPA/Ceria막의 합성 및 특성 연구

CL-SPEEK/Cs-TPA/CeO2 composite membrane was prepared for polymer electrolyte membrane water electrolysis (PEMWE). In order to improve the electrochemical, mechanical, durabilities and electrocatalytic characteristics, engineering plastic of polyether ether ketone (PEEK) as polymer matrix was sulfonated and the organic-inorganic blend composite membranes was prepared by loading cesium-substituted tungstophosphoric acid (Cs-TPA) by titration method with cross-linking agent contents of 0.01mL. Ceria (CeO2) was used to scavenge free radicals which attack the membrane in the PEMWE circumstance and to increase the duration of the membrane. In conclusion, CL-SPEEK/Cs(1)-TPA/Ceria 1% membrane showed the optimum results such as 0.119 S/cm at 80°C of proton conductivity and 62MPa of tensile strength.

Proton conducting, composite sulfonated polymer membrane for medium temperature and low relative humidity fuel cells

Inorganic–organic composite membranes are fabricated using zirconium acetylacetonate nanoparticles and biphenol-based sulfonated poly(arylene ether sulfone) as an inorganic, proton conducting nanomaterial and a polymer matrix, respectively. An amphiphilic surfactant (Pluronic®) induces distribution of the inorganic nanoparticles over the entire polymer membrane. The composite membranes are thermally stable up to 200 °C. Zirconium acetylacetonate improves inter-chain interactions and the robustness of polymer membranes resulting in excellent membrane mechanical properties. In addition, composite membranes show outstanding proton conductivity compared to that of the pristine membrane at medium temperatures (80–120 °C) and low relative humidity (<50%) conditions. This improvement is due to the presence of acetylacetonate anions, which bind water molecules and act as an additional proton conducting site and/or medium. Therefore, the composite membranes significantly outperform the pristine membrane in fuel cell performance tests at medium temperatures and low relative humidity.

표면처리된 실리콘 카바이드 섬유 복합막의 고분자 전해질 막 연료전지 성능

The organic-inorganic composite membrane in polymer exchange membrane fuel cells (PEMFCs) have several fascinating technological advantages such as a proton conductivity, thermal stability and mechanical properties. As the inorganic filler, silicon carbide (SiC) fiber have been used in various fields due to its unique properties such as thermal stability, conductivity, and tensile strength. In this study, composite membrane was successfully fabricated by modified-silicon carbide fiber. Modified process, as a novel process in SiC, takes reaction by phosphoric acid after oxidation process (generated homogeniusly <TEX>$SiO_2$</TEX> layer on SiC fiber). The mechanical property which was conducted by tensile test of the 5wt% modified-<TEX>$SiO_2@SiCf$</TEX> composite membrane was better than that of Aquivion casting membrane as well as ion cxchange capacity(IEC) and proton conductivity. In addition, the single cell performance was observed that the 5wt% modified-<TEX>$SiO_2@SiCf$</TEX> composite membrane was approximately <TEX>$0.2A/cm^2$</TEX> higher than that of a Aquivion casting electrolyte membrane and electrochemical impedance was improved with the charge transfer resistance and membrane resistance.

Cs 치환에 따른 수전해용 공유가교 SPEEK/Cs(n)-MoPA/Ceria 1%(n = 1~3) 복합막의 특성 연구

Ceria (<TEX>$CeO_2$</TEX>) was used to scavenge free radicals which attack the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance and to increase the duration of the membrane. In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of the sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) and the organic-inorganic blended composite membranes were prepared by sol-gel casting method with loading the highly dispersed ceria and cesium-substituted phophomolybdic acid(Cs-MoPA) with cross-linking agent contents of 0.01mL. In conclusion, CL-SPEEK/<TEX>$Cs_{(2.5)}$</TEX>-MoPA/ceria(1%) membrane showed the optimum results such as 0.1095S/cm of proton conductivity at <TEX>$80^{\circ}C$</TEX>, 2.906meq./g-dry-membrane of ion exchange capacity and mechanical characteristics, and 49.73MPa of tensile strength which were better than Nafion 117 membrane.

Fabrication, characterization, transportation of ions and antibacterial potential of polystyrene based Cu3 (PO4)2/Ni3 (PO4)2 composite membrane

Novel organic–inorganic composite membrane was successfully prepared by sol–gel process. Such composite membrane shows best thermal, mechanical and chemical stability as well as good ion exchange property. Structural configuration of membrane was confirmed by TEM, XRD and FTIR analysis while thermal properties examined by TGA/DTA and LCR analysis. Teorell, Meyer Siever, method was used to determine the theoretical values of potential. The observed potentials and charge densities seems to follow KCl<NaCl<LiCl and LiCl<NaCl<KCl order respectively. By potential observation transport number, mobility ratio, distribution coefficient, charge effectiveness and fixed charge density of ions were calculated very easily.

Poly(vinylidene fluoride)/poly(acrylic acid)/calcium carbonate composite membranes via mineralization

Organic–inorganic composite membranes were prepared via calcium carbonate (CaCO3) mineralization induced by poly(vinylidene fluoride) (PVDF)/poly(acrylic acid) (PAA) blend membranes. PAA was used as a polyanionic macromolecule in the blend membranes to generate CaCO3 particles by an alternate soaking process (ASP). The mineralization condition was optimized based on the concentrations of calcium chloride (CaCl2) and sodium carbonate (Na2CO3) solutions used for ASP, the number of ASP cycles, and the PAA content in the blend membranes. Structures and surface hydrophilicity of the composite membranes were characterized in detail by FTIR-ATR, FESEM, EDX, XRD and water contact angle. Results confirm that CaCO3 particles consisting of calcite and vaterite dispersed uniformly in/on the membranes. The membrane hydrophilicity increased dramatically due to the intrinsic wettability of these CaCO3 particles. In addition, the CaCO3 particles also caused the collapse of PAA chains in the membrane pores. Therefore, pure water fluxes of the membranes were improved about three times. Furthermore, the mineralized membranes even showed a high rejection (99.85%) of Congo red, which makes them potential in dye-polluted wastewater treatment.

Influence of the size and shape of silica nanoparticles on the properties and degradation of a PBI-based high temperature polymer electrolyte membrane

The life time stability of membrane material is one of the major parameters regarding reliability of high temperature polymer electrolyte membrane fuel cells. Present work has improved fuel cell durability and chemical stability by incorporating cross-linked silica particles in phosphoric acid doped poly(2,2′-m-phenylene-5,5′-bibenzimidazole) membranes. Three different silica particle contents were generated in membranes by in-situ sol–gel reaction from the precursor tetraethoxy silane and cross-linked to the polymer chains by using (3-glycidoxypropyl)-methyldiethoxysilane. The size, shape and distribution of the silica nanoparticles were examined by transmission electron microscopy. The amorphous characteristics and the chemical composition of the silica particles were investigated using X-ray diffraction, electron diffraction and energy dispersive X-ray spectroscopy. Detailed statistical analysis showed that by increasing the tetraethoxy silane content, the particle size was reduced while the amount of particles was increased. Ex-situ membrane characterization and in-situ membrane electrode assembly testing revealed a high influence of the silica content on the mechanical stability and start–stop-cycling behavior. The improved lifetime durability of the organic–inorganic composite membrane was proven in comparison to the pure polybenzimidazole membrane in membrane electrode assemblies over 1300h under constant fuel cell operation in reformate.

Novel method for incorporating hydrophobic silica nanoparticles on polyetherimide hollow fiber membranes for CO2 absorption in a gas–liquid membrane contactor

In a gas–liquid membrane contactor, a larger pore size can result in a lower membrane mass transfer resistance. However, the membrane pore size is usually limited by the concern of pore wetting, e.g. a large pore size means a higher wetting tendency. As a breakthrough, this paper reported a porous polyetherimide (PEI) hollow fiber membrane with high surface porosity and large pore size to minimize the membrane mass transfer resistance by using a triple-orifice spinneret in the hollow fiber spinning process, and followed by a novel approach of fluorinated silica (fSiO2) nanoparticles (NPs) incorporation to make the membrane surface highly hydrophobic and chemical resistant to prevent the membrane from wetting caused by the large pore size on the membrane surface. The newly developed composite hollow fiber membranes showed the advancing contact angle value of 123.3°, receding contact angle value of 107.2°, and contact angle hysteresis of only 15.9°, indicating the high water resistant property. The composite membrane also exhibited a higher rigidity property compared with the original PEI substrate. The CO2 absorption flux of the composite membranes was investigated in both physical and chemical absorptions in a gas–liquid membrane contactor system. The membrane contactor showed a stable performance throughout the 60d long-term operation using a 2M sodium taurinate aqueous solution as the liquid absorbent.The highly hydrophobic composite hollow fiber membrane was able to outperform a conventional polymeric hydrophobic membrane in term of superior gas absorption flux and outstanding long-term stability, suggesting that the formation of organic–inorganic composite membranes is an effective way to enhance the feasibility of membrane contactor processes for practical applications. The results demonstrated the important role of membrane fabrication and modification techniques in facilitating the commercialization of membrane contactor technology.

Influence of monovalent electrolytes on the electrochemical studies of newly synthesized thermally stable inorganic–organic nanocomposite membrane

A nanostructured inorganic–organic composite membrane has been synthesized by cost effective sol–gel method under acidic conditions. Membrane potential measurements have been carried out in various monovalent electrolytes (KCl (aq), NaCl (aq), etc.) at different concentrations to scrutinize the relationship between fixed charge concentration and electrochemical properties of the membrane. Effective fixed charge densities are found to follow the order: Li+>NH4+>K+>Na+. The calculated values of permselectivity, ionic mobility ratio and counter-ion transport number reveal that the inorganic–organic nanocomposite membrane is more cation-selective towards Li+ ions; however the selectivity decreases with the increase in concentration for all monovalent electrolytes used. These membranes were comprehensively characterized for their physicochemical properties, morphology, molecular interactions, crystallinity and thermal stability by various analyses. The ion-exchange capacity, volume void porosity and water uptake of the membrane are found to be highly dependent on polystyrene content in the membrane phase and these properties decrease with the increase in the amount of polystyrene. Furthermore, membrane with 25% blend ratio with polystyrene is found to exhibit good selectivity along with moderate ion-exchange capacity, which may be used for their application in electro-driven separation at high temperatures or for other electrochemical processes.

Fe0.4Ta0.5P2O7-based composite membrane for high-temperature, low-humidity proton exchange membrane fuel cells

An inorganic–organic composite membrane composed of Fe0.4Ta0.5P2O7 (FTPO) and sulfonated polystyrene-b-poly(ethylene/butylene)-b-polystyrene (sSEBS) is prepared and characterized. To gain satisfaction of both the proton conductivity and mechanical strength in composite membranes, the optimal content of sSEBS was determined to be 30wt%, which resulted in high proton conductivities of approximately 0.01Scm−1 between 50 and 150°C even under an unhumidified condition, a tensile strength of 4.1MPa, and an elongation at break of 613%. A homogeneous distribution of the FTPO particles in the matrix was achieved at the composite membrane thickness greater than 50μm, providing gas-impermeability and low area-specific resistance (ASR) of the membrane (0.17Ωcm2 at 150°C and H2O vapor concentration of 30.8vol%). Fuel cell tests using the composite membrane provided peak power densities of 265 and 303mWcm−2 at 150°C under an unhumidified condition and at a H2O vapor concentration of 30.8vol%, respectively.

Synthesis, characterization and influence of electrolyte solutions on electrical properties of organic–inorganic composite membrane

In this work various electrical properties of titanium molybdate composite membrane had been discussed. The membrane was characterized by X-ray diffraction, scanning electron microscopy, particle size analysis and Infra-red spectroscopy. The effective fixed charge density of the membrane was determined by TMS method and it showed the dependence of membrane potential on, the charge on the membrane matrix, porosity and size of permeating ions. The change in membrane capacitance and resistance values with the change in electrolyte concentration and applied frequency had been interpreted in terms of the charges produced in the electrical double layer at the membrane solution interface. The magnitude of membrane capacitance had been found to be dependent on the capacitance of the double layer. In higher frequency range the impedance data evaluated on the basis of simple equivalent electrical circuit model and had been found to follow theoretical prediction. Other parameters such as transport number, distribution coefficient and charge effectiveness were also calculated.

Solvent‐resistant nanofiltration membranes based on multilayered polyelectrolytes deposited on silicon composite

AbstractAlternating deposition of oppositely charged polyelectrolyte complexes (PECs) on inorganic–organic composite membranes can efficiently overcome the drawback of microcracks induced by inorganic particles. Different bilayers of Poly (diallyldimethylammonium, chloride)/sulfonated poly(ether ether ketone) (PDDA/SPEEK) were first deposited on the charged silicon composite with hydrolyzed polyacrylonitrile (PAN‐H) support and evaluated for solvent resistant nanofiltration membranes (SRNF) application. The morphology of the membranes was studied in detail via SEM and AFM. Because of Donnan exclusion, the multilayered PEC silicon composite membranes showed very high retentions up to 99% for negatively charged solutes (Rose Bengal (RB), 1017 Da) in the pressure driven filtration of isopropanol (IPA) solutions. For the first time, PEC‐based silicon composite membranes were also applied in the filtration of organic solvents, where they were found to combine a remarkable stability in polar solvents with high fluxes and retentions. Compared with silicon composite membranes, the introduction of multilayered PDDA/SPEEK can efficiently improve the membrane performance and overcome the drawback induced by inorganic fillers. PEC‐based silicon composite membranes thus show excellent prospective use in SRNF. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Characterization, Physicochemical Properties and Transport Studies of Newly Synthesized Polystyrene Blended Inorganic-Organic Nanocomposite Membrane

A nanostructured polystyrene based inorganic-organic composite membrane has been synthesized by sol-gel method under acidic conditions. Investigation on the electrochemical properties showed that higher membrane potential was observed in case of LiCl than other electrolytes used such as NH4Cl, KCl and NaCl for the nanocomposite membrane. Effective fixed charge densities were evaluated from the measured potential and were found to follow the order Li+ > NH4+ > K+ > Na+. The permselectivity, ionic mobility ratio and counter-ion transport number of the composite membrane have also been calculated which suggest that the inorganic-organic nanocomposite membrane is more cation-selective towards Li+ ions; however the selectivity increases with dilution for all monovalent electrolytes. These membranes were comprehensively characterized for their physicochemical properties, morphology, molecular interactions, crystalline nature and thermal stability by water uptake and porosity studies, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray studies, thermogravimetric and differential thermal analyses (TG-DTA). The ion-exchange capacity, volume void porosity and water uptake of the membrane were found to be highly dependent on polystyrene content in the membrane phase and these properties decreased with increase in the amount of the organic polymer.

수전해용 공유가교 SPEEK/Cs-TPA/Ceria 복합막의 제조 및 특성 연구

Abstract >> Ceria (CeO 2 ) was used to scavenge free radicals which attack the membrane in the polymer electrolytemembrane water electrolysis (PEMWE) circumstance and to increase the duration of the membrane. In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of the sulfonatedpolyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) and the organic-inorganic blended composite membranes were prepared by sol-gel casting methodwith loading the highly dispersed ceria and cesium-substituted tungstophosphoric acid (Cs-TPA) with cross-linkingagent contents of 0.01 mL. In conclusion, CL-SPEEK/Cs-TPA/ceria (1%) membrane showed the optimum results such as 0.130 S/cm of proton conductivity at 80℃, 2.324 meq./g-dry-membrane of ion exchange capacity and mechanical characteristics, and 65.03 MPa of tensile strength which were better than Nafion 117 membrane. Key words : Ceria(Cerium(IV) oxide, 세리아), SPEEK(술폰화 폴리에테르에테르케톤), PEMWE(고분자 전해질막 수전해), Covalently cross-link(공유가교결합), Cs-TPA(Cs-substituted TPA), Oxidative stability(산화내구성), Radical scavenger(라디칼 스캐빈져)

Crosslinked sulfonated poly(arylene ether sulfone)/silica hybrid membranes for high temperature proton exchange membrane fuel cells

Sulfonated poly(arylene ether sulfone) copolymer is synthesized via nucleophilic step polymerization of sulfonated 4,4′-dichlorodiphenyl sulfone, 4,4′-dichlorodiphenyl sulfone and phenolphthalin monomers in the presence of potassium carbonate. The copolymer is blended with various amounts of silica particles to form organic–inorganic composite membranes. Esterification reaction is carried out between silica particles and the sulfonated polymer chains by thermal treatment in the presence of sodium hypophosphite, which catalyzed the esterification reaction. The composition and incorporation of the sulfonated repeat unit are confirmed by 1H NMR. The water uptake, proton conductivity, and thermal decomposition temperature of the membranes are measured. The silica content in the polymer matrix and the effect of esterification are evaluated. All composite membranes show better water uptake and proton conductivity than the unmodified membrane. Moreover, the membranes are tested in a commercial single cell at 80 °C and 120 °C in humidified H2/air under different relative humidity conditions. The composite membrane containing 10% (w/w) silica shows the best performance among the prepared membranes especially under high temperature and low humidity conditions.

Properties of SPAES/phosphotungsticacid/sulfonated silica composite membranes prepared by the In situ and sol-gel process

An in situ sol-gel method was used to synthesize organic-inorganic composite membranes based on poly(arylene ether sulfone) (SPAES), phosphotungstic acid (PWA), and sulfonated silica (silica-SO3H). The PWA particles were functionalized with an organic silane compound to enhance proton conductivity. This study compares the performance of polymer electrolyte membrane fuel cells with different preparation methods for the membrane and composite of PWA-silica-SO3H particles. The optimum composition of PWA-silica-SO3H is determined on the basis of the mechanical properties, the behavior of water in the membrane, and the level of proton conductivity. The mechanical properties of the sol-gel composite membranes were improved with the introduction of PWA-silica-SO3H particles. The sol-gel composite membrane has higher levels of proton conductivity than the in situ composite membrane and pure SPAES membrane. An increase in the silica content of the PWA-silica sol-gel particles increases the proton conductivity because the inorganic component and the incorporation of PWA lead to a high concentration of hydroxyl groups. These properties make composite membranes potential candidates for direct methanol fuel cell applications. Open image in new window

Study on a novel composite membrane for treatment of sewage containing oil

When treated with sewage, polysulfone (PSF) membranes have a tendency to be contaminated due to their hydrophobicity, which limits large scale applications. To enhance the hydrophilic and anti-fouling property of PSF membrane, a novel organic–inorganic composite membrane was prepared by adding sulfated Y-doped nonstoichiometric zirconia (zirconia with defects, ZD) to PSF through a sol–gel process. The composite membranes were exposed to sewage containing oil, and the effects of the added amount of ZD, oil concentration, operating pressure, temperature and time on properties of composite membrane were researched. The optimum parameters are: 15wt.% added ZD; 80mg/L oil concentration; 0.15MPa operating pressure; operating temperature between 22 and 30°C and up to 5h of operating time. At 80mg/L sewage containing oil, the oil retention is 99.16% and the oil concentration in the permeate is 0.67mg/L, which meets the requirement for discharge (less than 10mg/L). After backflushing and chemical cleaning, the composite membranes could still keep a high permeation flux. It can be concluded that the hydrophilic and anti-fouling property of composite membrane can be significantly enhanced and hence the novel composite membrane is desirable in the treatment of sewage containing oil.

Electrochemical characterization and transport properties of polyvinyl chloride based carboxymethyl cellulose Ce(IV) molybdophosphate composite cation exchange membrane

The polyvinyl chloride (PVC) based carboxymethyl cellulose Ce(IV) molybdophosphate composite membrane are prepared and characterized by the Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR), and thermogravimetric analysis (TGA) studies. The inorganic–organic composite membrane was found to be crystalline in nature with consistent arrangement of particles and indicating no sign of visible cracks. The FTIR spectra verify the binding of organic polymer with inorganic component. The membrane was found to be cation-selective. The order of surface charge density for uni-univalent electrolytes solution was found to be KCl>NaCl>LiCl.