Synthesis of organic-inorganic composite membrane by sol-gel process

Silica was succesfully incorporated into cation exchange polymer membranes, CL-25T and Nafion 417, utilizing sol-gel process. As dipping time increased, increase in silica uptake in membrane was observed. In Nafion 417 membrane, no relationship was found between the silica uptake and the change in ion exchange capacity. But CL-25T which has larger pores than Nafion 417 shows proportional decrease in ion exchange capacity with increasing silica uptake. It suggests that the pore structure of membrane and the size control of silica sol are important to modify the structure of composite membranes. In CL-25T membranes modified by silica, the transport rate of IPA (isopropyl alcohol) increased with increasing OH^- concentration on the pore surface.     

Transport Properties of Ion‐Exchange Membranes During Pervaporation of Water‐Alcohol Mixtures

Abstract

Pervaporation properties of PESS ion‐exchange membranes in contact with water‐aliphatic alcohol mixtures were obtained. PESS ion‐exchange membranes were prepared by chemical modification of the interpenetrating polymer network system polyethylene‐poly(styrene‐co‐divinylbenzene). PESS membranes were loaded with different alkali metal ions as counterions. The obtained data showed that properties of PESS membranes depended strongly on the kind of counterions, degree of crosslinking, and difference in the polarities between water and organic component of the binary mixture. Results obtained for PESS membranes were compared with data obtained for Nafion 117 ion‐exchange membrane.     

Novel grafted nafion membranes for proton‐exchange membrane fuel cell applications

Novel poly(glycidyl methacrylate)‐grafted Nafion–phosphoric acid membranes for direct‐oxidation methanol fuel cells were prepared with a potassium persulfate chemical initiation system for the first time. The introduced epoxy groups were converted to amine groups through a reaction with ethylenediamine, which consequently doped with phosphoric acid ( PO₃H) groups. The latter significantly contributed to enhancing the ion‐exchange capacity, mechanical properties, and thermal stability. Factors affecting the modification steps were studied. Changes in the chemical and morphological structure were verified through Fourier transform infrared spectroscopy, TGA, and scanning electron microscopy characterization. Various grafting percentages (GP%'s) up to 32.31% were obtained. As a result, the thickness of the grafted membranes increased. Furthermore, the methanol permeability of the modified membranes was reduced with increasing grafted polymer content compared with that of the Nafion membrane. An 83.64% reduction in the methanol permeability was obtained with a polymer grafted content of 18.27%. Finally, the efficiency factor for all of the modified Nafion membranes was enhanced compared with that of Nafion. A fourfold improvement was obtained with membranes with a GP% of 18.27% as a maximum value. Such promising results nominate the used technique as a one for the improvement of Nafion membrane efficiency. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Modification of Nafion membranes with ternary composite materials for direct methanol fuel cells

Composite membranes for direct methanol fuel cells (DMFCs) were prepared by using Nafion115 membrane modification with polyvinyl alcohol (PVA), polyimide (PI) and 8-trimethoxysilylpropyl glycerin ether-1,3,6-pyrenetrisulfonic acid (TSPS). The performance of the composite membranes was evaluated in terms of water sorption, dimensional stability, thermal stability, proton conductivity, methanol permeability and cell performance. The proton conductivity was slightly decreased by 1-3% compared with Nafion115, which still kept the high proton conduction of Nafion115. The methanol permeability of Nafion/PI-PVA-TSPS composite membranes was remarkably reduced by 35-55% compared with Nafion115. The power density of DMFCs with Nafion/PI-PVA-TSPS composite membranes reached to 100 mW/cm², exceeding that with Nafion115 (68m W/cm²).     

The influence of poly(3,4-ethylenedioxythiophene) modification on the transport properties and fuel cell performance of Nafion-117 membranes

Nafion-117/PEDOT composite membranes were synthesized by in situ chemical polymerization of 3,4-ethylenedioxythiophene (EDOT) using ammonium persulfate as an oxidant. The polymerization of EDOT in Nafion membranes for various EDOT/oxidant treatment sequences was studied for the first time. PEDOT introduction leads to a slight decrease in both the ion-exchange capacity and water uptake of the composite membranes, as well as to an increase in cationic transport. Membranes initially treated with an oxidant exhibit better conductivity and lower hydrogen permeability. The effect of both modification of Nafion-117 membranes by PEDOT and hot-pressing of hydrogen-oxygen membrane-electrode assemblies (MEAs) on the performance of proton-exchange membrane fuel cells was studied. The maximum power density of the fabricated MEAs increases 1.5-fold: from 510 (for a pristine Nafion-117 membrane) to 810 mW cm⁻² (for a membrane modified by PEDOT). The current density at a voltage of 0.4 V reaches 1248 and 2246 mA cm⁻², respectively.     

Solution‐blown SPEEK/POSS nanofiber–nafion hybrid composite membranes for direct methanol fuel cells

This study aims to develop novel hybrid composite membranes (NHMs) by impregnating Nafion solution into the porous sulfonated poly(ether ether ketone)/polyhedral oligomeric silsesquioxanes (SPEEK/POSS) nanofibers (NFs). The composite membrane was prepared by solution blowing of a mixture of SPEEK/POSS solution. The characteristics of the SPEEK/POSS NFs and the NHMs, including morphology, thermal stability, and performance of membrane as PEMs, were investigated. The performance of NHMs was compared with that of Nafion117 and SPEEK/Nafion composite membranes. Results showed that the introduction of POSS improved the proton conductivity, water swelling, and methanol permeability of membranes. A maximum proton conductivity of 0.163 S cm^?1 was obtained when the POSS content was 6 wt % at 80°C, which was higher than that of Nafion117 and SPEEK/Nafion. NHMs could be used as proton exchange membranes (PEMs) for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42843.     

Transport of proton in polymeric ionic exchange membranes in relation with the dissociated sorbed acid

The transport of proton in ion exchange membranes in contact with HCl and H₂SO₄ solutions is studied. The membranes are the Nafion® 117 cation exchange membrane and, on the other hand, the Selemion® AAV and the Morgane ARA anion exchange membranes. Sorption and water content measurements combined with the radiotracer technique point out the low dissociation degree of the acid present in the membrane phase. This low dissociation leads to the excellent permselectivity towards proton of the Nafion membrane, and it is also the factor which decreases the proton leakage in the two studied anion exchange membranes.     

Impact of Mesoporous and Microporous Materials on Performance of Nafion and SPEEK Polymer Electrolytes: A Comparative Study in DEFCs

Hybrid membranes are prepared from fluoro and non‐fluoro polymer membrane matrices with mesoporous and microporous inorganic materials. Nafion‐Si‐MSU‐F, Nafion‐Al‐MCM‐41, and zeolite 4A‐SPEEK‐MSA hybrid membranes are fabricated by solution casting method. The structural properties of the membranes are characterized using FE‐SEM and AFM techniques. Ion exchange capacity, sorption, proton conductivity, and thermal stability for the membranes have been extensively investigated. Ethanol permeability measurements for the membranes are performed using electrochemical as well as diffusion cell method. Among the membranes that are tested in direct ethanol fuel cells (DEFCs), Nafion‐Al‐MCM‐41 hybrid membrane delivered the highest peak power‐density of 44 mW cm^–2 at 70 °C.     

CHITOSAN-BASED FUEL CELL MEMBRANES

Chitosan complex membranes are prepared and characterized at room temperature. They are expected to be used as proton exchange membranes. The studied membranes are cross-linked membranes with sulfuric acid; salt-complexed membranes with lithium nitrate; cross-linked and salt-complexed membranes; plasticized and salt-complexed membranes; cross-linked, plasticized, and salt-complexed membranes; and doped membranes with sulfuric acid. A fixed amount of ethylene carbonate is used as plasticizer. It is found that the ion exchange capacity and hydrogen gas permeability of all membranes is better than that of Nafion membranes. However, their proton conductivities are worse than Nafion membranes. It can be stated that ethylene carbonate does not improve conductivity. An optimum amount of lithium nitrate salt can enhance conductivity. The formation of a sulfate group in cross-linked membranes is necessary for proton conduction. The proton conductivities of 4%cross-linked and 50%LiNO₃ membrane before and after acid doping are (3.11±0.40) × 10^?2 and (6.64±0.11) × 10^?2 S cm^?1, respectively. That of Nafion is (8.02±1.19) × 10^?2 S cm^?1.     

Application of sodium conducting membranes in direct methanol alkaline fuel cells

A study of a direct methanol alkaline fuel cell (DMAFC) operating with sodium conducting membranes is reported. Evaluation of the fuel cell was performed using membrane electrode assemblies incorporating carbon supported platinum catalysts and Nafion^® 117 and 112 membranes. A membrane electrode assembly was also prepared by the direct chemical deposition of platinum into the surface region of the membrane. Evaluation of the chemically deposited assembly showed it to be less active than those based on carbon supported catalysts. SEM &; TEM analysis indicate that this behaviour is due to the low surface area of the chemically deposited catalyst layer. The fuel cell performance with Nafion membranes is reported and is not as good as achieved with hydroxide ion conducting membranes suggesting that Nafion may not be suitable for DMAFC operation.     

Preparation and characterization of novel grafted cellophane‐phosphoric acid‐doped membranes for proton exchange membrane fuel‐cell applications

This work concerns preparation of acid‐base polyelectrolyte membranes for fuel‐cell applications from cellulosic backbones for the first time. Grafted cellophane‐phosphoric acid‐doped membranes for direct oxidation methanol fuel cells (DMFC) were prepared following three steps. The first two steps were conducted to have the basic polymers. The first step was introducing of epoxy groups to its chemical structure through grafting process with poly(glycidylmethacrylate) (PGMA). The second step was converting the introduced epoxy groups to imides groups followed by phosphoric acid (? PO₃H) doping as the last step. This step significantly contributes to induce ion exchange capacity (IEC) and ionic conductivity (IC). Chemical changes of the cellophane composition and morphology characters were followed using FTIR, TGA, and SEM analysis. Different factors affecting the membranes characters especially IEC, methanol permeability, and thermal stability were investigated and optimized to have the best preparation conditions. Compared to Nafion 117 membrane, cellophane‐modified membranes show a better IEC, less methanol permeability, and better mechanical and thermal stability. IEC in the range of 1–2.3 meq/g compared to 0.9 meq/g per Nafion was obtained, and methanol permeability has been reduced by one‐order magnitude. However, the maximum obtained IC for cellophane‐PGMA‐grafted membrane doped with phosphoric acid was found 2.33 × 10^?3 (S cm^?1) compared to 3.88 × 10^?2 (S cm^?1) for Nafion 117. The obtained results are very promising for conducting further investigations taking into consideration the very low price of cellophane compared to Nafion. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Modification and evaluation of membranes for vanadium redox battery applications

Several commercial ion exchange membranes were evaluated for application in the vanadium redox battery. The polyether membrane, DF120 cationic exchange membrane, showed the highest permeability to vanadium ions and the worst chemical stability in V(V) solution, while the divinylbenzene membrane, JAM anionic exchange membrane, showed the lowest permeability to vanadium ions and the best chemical stability in V(V) solution. In order to impart some cationic exchange capacity to the JAM anionic exchange membrane, sodium 4-styrenesulfonate was used to modify the anionic membrane by in situ polymerization. Measurements by infrared spectroscopy (IR) and cationic ion exchange capacity (IEC) verified that the modification procedure imparts cationic exchange capability to the membrane. Incorporation of cationic exchange groups to the anionic exchange membrane further results in a reduction in permeability to vanadium ions. The current and energy efficiencies averaged over 8 charge/discharge cycles of the cell with the treated JAM membrane were higher than that with the untreated JAM membrane. The current and energy efficiencies of the cell with the treated JAM membrane did not change over several charge/discharge cycles, which indicates good chemical stability of the treated membrane in the vanadium redox cell. The average efficiencies of the cell with the treated JAM membrane are higher than that with Nafion 117 over 8 charge/discharge cycles.     

聚吡咯修饰Nafion膜直接甲醇燃料电池的性能

用FeCl3化学氧化法制备了PPy/Nafion改性膜,采用浸渍-还原法在PPy/Nafion阴极侧上沉积Co金属,制得Co-PPy/Nafion电解质膜。采用TG、CV及交流阻抗谱测试了Nafion膜及改性膜的热稳定性,质子电导性和甲醇渗透性能,结果表明:PPy/Nafion及Co-PPy/Nafion改性膜具有更好的热稳定性和抗甲醇渗透性。分别以Co-PPy/Nafion改性膜、PPy/Nafion改性膜和纯Nafion膜为电解质膜,PtRu/C为阳极催化剂,Pt/C为阴极催化剂组装DMFC并考察其性能。实验结果表明:Co-PPy/Nafion改性膜组装单电池在高浓度甲醇及大电流密度的测试条件下,表现出更优异的电池性能。     

Nafion 115/zirconium phosphate composite membranes for operation of PEMFCs above 100 °C

Composite Nafion/zirconium phosphate membranes were investigated for high temperature operation of proton exchange membrane fuel cells (PEMFCs). The composite membranes were prepared via impregnation of Nafion films (either commercial Nafion 115 or recast Nafion) with zirconyl chloride and 1 M phosphoric acid at 80 °C. An MEA employing a composite membrane prepared starting from commercial Nafion 115 gave a H₂/O₂ PEMFC performance of about 1000 mA/cm² at 0.45 V at a temperature of 130 °C and a pressure of 3 bar; this result compares very favorably with the performance of an MEA based on commercial unmodified Nafion, which gave only 250 mA/cm² at 0.45 V when operated under the same conditions of temperature and pressure. Similar experiments performed with recast Nafion and recast Nafion/zirconium phosphate composites confirmed an analogous improvement of performance of the composite membranes over the unimpregnated ones. In this case, the composite recast Nafion/zirconium phosphate gave about 1500 mA/cm² at 0.45 V at a temperature of 130 °C and a pressure of 3 bar. The composite membranes showed stable behavior during time when maintained at 130 °C, while irreversible degradation affected Nafion under the same conditions.     

全钒液流电池用磺化聚芴醚酮质子交换膜的制备及性能

质子交换膜(PEM)作为全钒液流电池(VRFB)的核心组件之一,应当解决成本高昂、合成过程复杂等问题,并具备高质子传导率、低钒离子渗透率、高机械强度和优异化学稳定性等关键性能。本文基于四甲基双酚芴单体通过缩聚反应合成了一系列聚芴醚酮化合物PFEKs,再利用溴代反应将苯甲基功能化为溴甲基,接着通过4-羟基苯磺酸钠的SN₂亲核取代制得了一系列不同离子交换容量的磺化聚芴醚酮聚合物(SPFEKs)。通过溶液浇铸法成膜并酸化,得到一系列新型低成本PEMs。该合成路线的原料来源广泛,价格低廉,不涉及危险的磺化反应,易于工业放大。所得膜都具有良好的机械性能和氧化稳定性,其中SPFEK-40膜具有较高的质子传导率及离子选择性、较低的钒离子渗透率及面电阻,综合性能优异。以SPFEK-40膜组装的VRFB在电流密度为80 mA/cm₂^{时的能量效率}(EE)为88.2%,高于以Nafion 212膜组装的VRFB的84.8%。此外,以SPFEK-40膜组装的VRFB在30次循环后放电容量仅衰减至84.3%,远高于以Nafion 212膜组装的VRFB的66.1%。     

Nafion‐115/aromatic poly(etherimide) with isopropylidene groups/imidazole membranes for polymer fuel cells

Proton exchange membrane fuel cells (PEMFCs) with Pt/C gas diffusion electrodes and graphite single‐serpentine monopolar plates were constructed based on an aromatic poly(etherimide) with isopropylidene groups (PI)/imidazole (Im) and a popular Nafion‐115 matrix. The electrochemical properties of PEMFCs were tested at 25 and 60°C. The maximum power density of 171 mW/cm² and the maximum current density of 484 mA/cm² were detected for Nafion‐115/PI membrane. For both constructed PEMFCs the efficiency at 0.6 V was found about 41%. Immersion of Nafion‐115 in PI or PI/Im increased the thermal stability and mechanical properties of membranes. Thermal, mechanical properties and morphology of membranes were characterized by TGA, and AFM techniques including force spectroscopy. Interactions between the components in composite membranes were established by FT‐IR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42436.     

Fabrication and characterization of PFSI/ePTFE composite proton exchange membranes of polymer electrolyte fuel cells

PFSI/ePTFE composite proton exchange membranes were fabricated by impregnating perfluorosulfonic acid resin (PFSI resin, Nafion) into chemically modified expanded PTFE (ePTFE) matrix. Chemical modification of sodium-naphthalene treatment and N-methylol acrylamide (NMA) grafting decreased the contact angle of the as-received ePTFE from 125 ± 0.5° to 67 ± 0.5°, effectively converting the as-received hydrophobic ePTFE to a hydrophilic ePTFE matrix. The composite membrane fabricated with the hydrophilic ePTFE have higher impregnated PFSI loading, much lower porosity and better PTFE/PFSI interface contact, as compared to the composite membranes with the as-received ePTFE. This leads to much lower gas permeability and significantly improves the durability under an accelerated dry/wet cycle test. The fuel cell made from the PFSI/ePTFE composite membranes with hydrophilic ePTFE showed superior performance as compared to that with the composite membrane made from the as-received ePTFE and Nafion 211 membrane.     

Studies of a high temperature proton exchange membrane based on incorporating an ionic liquid cation 1-butyl-3-methylimidazolium into a Nafion matrix

High temperature proton exchange membranes based on Nafion were prepared by incorporating the polymer with ionic liquid cation 1-butyl-3-methylimidazolium (BMIm) and doping with phosphoric acid (PA). We found that using the hydroxide form rather than the chloride form of BMIm incorporated more readily the BMIm cation into Nafion film. A mole ratio of about 2 of BMIm cation to Nafion repeat unit, i.e., λ_BMIm/Nafion, was reached with the hydroxide form BMIm. The incorporated BMIm cation enhanced the doping of phosphoric acid into Nafion. A proton conductivity of 10.9 mS cm⁻¹ and a tensile stress at break of 5.3 MPa were achieved, respectively, with a composite membrane of Nafion/2.3BMIm/5.2PA in molar ratio at 160 °C without humidification.     

Nafion®—titania nanocomposite proton exchange membranes

Proton exchange membranes consisting of Nafion^® and crystallized titania nanoparticles have been developed to improve water‐retention and proton conductivity at elevated temperature and low relative humidity. The anatase‐type titania nanoparticles were synthesized in situ in Nafion solution through sol–gel process and the size of the formed titiania nanoparticles is in the range of 3–6 nm. The formed nanoparticles are well‐dispersed in Nafion solution at the titania concentration of 5 wt %. The glass transition temperature of the formed Nafion‐titania composite membrane is about 20^oC higher than that of plain Nafion membrane. At elevated temperature (above 100°C), the Nafion‐titania nanocomposite membrane shows higher water uptake ability and improved proton conductivity compared to pure Nafion membrane. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of Sulfonated Graphene Oxide on Sulfonated Polysulfone Membrane for Direct Methanol Fuel Cell

Novel proton exchange membranes consisting of an inorganic filler, namely sulfonated graphene oxide, embedded in sulfonated polysulfone were fabricated. The membrane performance depended on the sulfonated graphene oxide content possessed the functional groups to provide the interfacial interaction with sulfonated polysulfone through ionic channels and blocking effect. The membrane with 3% v/v sulfonated graphene oxide content embedded in the matrix was shown to be suitable for direct methanol fuel cell applications. The membrane exhibited the highest proton conductivity of 4.27?×?10^?3 S cm^?1 which was higher than that of Nafion117. Moreover, the membrane provided the lowest methanol permeability of 3.48?×?10^?7?cm²/s which was lower than that of Nafion117.