Proton Conductivity Of Composite Membranes Research Articles

Anchoring of Fe-MIL-101-NH2 to the Polymer Membrane Matrix through the Hinsberg Reaction to Promote Conductivity of SPEEK Membranes.

SCPEEK@MOF proton exchange membranes, where SCPEEK is sulfinyl chloride polyether ether ketone and MOF is a metal-organic framework, were prepared by doping Fe-MIL-101-NH2 into polymers. The amino group in the MOF and the -SOCl2 group in thionyl chloride polyether ether ketone cross-link to form a covalent bond through the Hinsberg reaction, and the prepared composite membrane has stronger stability than other electrostatic interactions and simple physical doping composite membranes. The formation of covalent bonds improves the water absorption of the composite membrane, which makes it easy for water molecules to form hydrogen bonds. Moreover, SPEEK as a proton conductive polymer and the synergy of MOFs improve the proton conductivity of composite membranes. The composite membranes were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The swelling rate, water absorption, mechanical stability, ion exchange capacity, and proton conductivity of the pure sulfonated polyether ether ketone (SPEEK) membrane were compared with those of the mechanically doped SPEEK/MOF membrane and the composite membrane SCPEEK@MOF doped with different ratios of Fe-MIL-101-NH2, and all of the SCPEEK@MOF showed superior performance. When the Fe-MIL-101-NH2 loading rate of the composite membrane is 2%, the proton conductivity of the composite membrane can reach 0.202 S cm-1 at 363 K and a 98% relative humidity, which is much higher than that of the SPEEK/MOF membrane obtained by simple physical doping under the same conditions.

The influence of polyvinyl alcohol concentration toward conductivity and permeability of chitosan - montmorillonite composite membrane

The composite membrane is synthesized using chitosan as a matrix membrane with montmorillonite (MMT) as a filler and modified using polyvinyl alcohol (PVA). The main aim of this study is to find out the influence of PVA concentration and the working temperature toward the permeability of chitosan?MMT/PVA composite membrane. Fourier transform infrared spectroscopy (FTIR) characterization is performed in order to identify the interaction between the chitosan matrix and the modified MMT with PVA. The presence of new absorption at 1116.82 and 619.17 cm-1 indicated the interaction between MMT and PVA. Further, the widening of OH absorption indicated the hydrogen bond which is formed between chitosan matrix and PVA. This interaction is also demonstrated by the evenly distributed surface on scanning electron microscope (SEM) topography analysis. The thermal stability of composite membrane is determined by thermal gravimetry analysis (TGA). In addition, the composite membrane containing PVA has four patterns decomposed. When the TVA is absent from the composite membrane, it has three decomposition patterns, which are shown by TGA analysis. Based on its tensile strength, the composite membrane has good mechanical properties. The proton conductivity of the composite membranes are directly proportional to the PVA concentration. On the other hand, the methanol permeability of composite membranes is inversely proportional with the PVA concentration. The highest proton conductivity was obtained with the addition of 2 % PVA of 2.94?10-4 S cm-1. Further, it also has the lowest methanol permeability with the value of 5.05?10-6 cm2 s-1. As a result, the crosslinked composite membrane chitosan? ?MMT prepared by PVA-crosslinking technique has the potential to be exploited for the direct methanol fuel cell application.

Enhancing Proton Conductivity of Nafion Membrane by Incorporating Porous Tb-Metal-Organic Framework Modified with Nitro Groups.

A rigid carboxylate ligand with a nitro functional group was selected to coordinate with Tb(III) cation, and Tb-MOF ({[Tb4(L)4(OH)4(H2O)3]·8H2O}n, H2L = 2-nitroterephthalic acid) with large porous and excellent hydrophilicity was obtained successfully. The obtained Tb-MOF was filled into the Nafion matrix to improve its proton conduction performance. The Tb-MOF/Nafion composite membrane was characterized by PXRD, IR, and thermogravimetry (TG) and for water uptake, area swelling, and proton conductivity. The activity energy, Ea, value of the composite membrane, which is a very important factor affecting the proton conduction performance of the membrane, was fitted and calculated. It was revealed that Tb-MOF can improve the proton conductivities of composite membranes, and the improvement degree and Ea value were both affected by Tb-MOF content. When Tb-MOF content was 5%, the proton conductivity of the composite membrane was 1.53 × 10-2 S·cm-1 at 100% RH and 80 °C, which is 1.81 times that of the pure Nafion membrane. A MOF containing a nitro functional group was first doped into Nafion in this study and exhibited excellent performance for improving composite membrane proton conductivity. This study will provide a valuable reference for designing different functionalized MOFs to promote the proton conductivities of proton exchange membranes.

Composite membrane by incorporating sulfonated graphene oxide in polybenzimidazole for high temperature proton exchange membrane fuel cells

The objective of this work is to examine the polybenzimidazole (PBI)/sulfonated graphene oxide (sGO) membranes as alternative materials for high-temperature proton exchange membrane fuel cell (HT-PEMFC). PBI/sGO composite membranes were characterized by TGA, FTIR, SEM analysis, acid doping&acid leaching tests, mechanical analysis, and proton conductivity measurements. The proton conductivity of composite membranes was considerably enhanced by the existence of sGO filler. The enhancement of these properties is related to the increased content of –SO 3 H groups in the PBI/sGO composite membrane, increasing the channel availability required for the proton transport. The PBI/sGO membranes were tested in a single HT-PEMFC to evaluate high-temperature fuel cell performance. Amongst the PBI/sGO composite membranes, the membrane containing 5 wt. % GO (PBI/sGO-2) showed the highest HT-PEMFC performance. The maximum power density of 364 mW/cm 2 was yielded by PBI/sGO-2 membrane when operating the cell at 160 °C under non humidified conditions. In comparison, a maximum power density of 235 mW/cm 2 was determined by the PBI membrane under the same operating conditions. To investigate the HT-PEMFC stability, long-term stability tests were performed in comparison with the PBI membrane. After a long-term performance test for 200 h, the HT-PEMFC performance loss was obtained as 9% and 13% for PBI/sGO-2 and PBI membranes, respectively. The improved HT-PEMFC performance of PBI/sGO composite membranes suggests that PBI/sGO composites are feasible candidates for HT-PEMFC applications. • This study proposes PBI/sGO as an alternative membrane for HT-PEMFC application. • SGO was revealed as an effective filler for a PBI composite membrane for HT-PEMFC. • PBI/sGO membranes possess high proton conductivity. • PBI/sGO membrane with 5% GO content is a potential electrolyte for HT-PEMFC.

Tuning proton conduction by different particle sizes in open-framework metal phosphates

The proton conductions of open-framework metal phosphates K2[(VO)2(HPO4)2(C2O4)] (KVPC) with large and small particle sizes, namely KVPC-L and KVPC-S, have been evaluated. Varied particle sizes result in different proton conductive behaviors. KVPC-S exhibits a high proton conductivity of 1.15 × 10−2 S cm−1 under 40 °C, 95% RH and possesses a stable proton conduction for 4 h. Furthermore, proton conductivities of composite membranes are investigated, and the value can reach up to 1.19 × 10-3 S cm−1 under 60 °C, 95% RH and remain no significant change within 6 h.

The preparation of novel sulfonated poly(aryl ether ketone sulfone)/TiO2 composite membranes with low methanol permeability for direct methanol fuel cells

A sulfonated poly(aryl ether ketone sulfone) (SPAEKS) with locally dense sulfonic acid groups is synthesized and different amounts of TiO2 is doped into SPAEKS matrix to prepare composite membranes (SPAEKS/TiO2-x). SEM shows that TiO2 in the composite membranes has good dispersibility when TiO2 content is not higher than 3%. The composite membranes show good mechanical properties, dimensional stability and oxidative stability. The proton conductivity of composite membranes is near to that of Nafion 117 membrane and methanol permeability of composite membranes is much lower than that of Nafion 117 membrane. Therefore, the proton selectivity of composite membranes is higher than that of Nafion 117 membrane. In particular, proton selectivity of SPAEKS/TiO2-3% (12.8 × 104 S s cm−3) is four times higher than that of Nafion 117 membrane (3.2 × 104 S s cm−3).

Effect of zeolite content on proton conductivity and technical characteristics of the membranes based on crosslinked polyvinyl alcohol

Polyvinyl alcohol (PVA)-based ion-exchange membranes are a promising group of materials for use in solid polymer fuel cells (SPFC) due to their high hydrophilicity, film forming ability, low cost, good mechanical properties and the possibility of crosslinking PVA with various chemicals. The compounds with a carboxyl or carbonyl functional group, such as polybasic acids and their anhydrides, were used as crosslinking agents resulting in the formation of a gel. Cross-linking reagents may contain ionic groups, for example, sulfonic, inducing the proton conductivity of PVA in membranes. Ceramic materials based on the oxides of aluminum, silicon, titanium, tin, zirconium, etc. serve as dopants in order to improve the technical characteristics of such membranes, such as to increase ionic conductivity, chemical and thermal stability, as well as the mechanical strength of the membranes. In this work, we report on the preparation of new biodegradable proton exchange membranes for SPFCs based on of polyvinyl alcohol crosslinked with sulfosuccinic acid and doped with beta zeolite particles. The content of zeolite in the composition of the membranes was varied from 1 to 25 %. The effect of the zeolite content on proton conductivity, ion-exchange capacity, moisture content, swelling coefficient, fuel (methanol) permeability and mechanical properties of membranes was studied. An increase in zeolite content from 1 to 25 % leads to an increase in the ion-exchange capacity of membranes from 1.5 to 2.9 mmol/g, a decrease in moisture content from 38 to 28 % and a methanol permeability from 2.27  10 -6 to 6.91  10 -7 cm 2 s -1 . The temperature dependence of the proton conductivity of composite membranes in the range from 30 to 80 oC at the relative humidity of 100 % was studied. The highest value of electrical conductivity was demonstrated by a membrane containing 25 % of BEA zeolite, whose proton conductivity was 23.2 mS·cm -1 .

A dual-functional metal phosphate for high proton conduction and selective luminescence turn-on sensing of Co2+ ions

The {[Zn(H2PIPZ)](H2O)}n (compound 1) detects Co2+ ions with turn on fluorescent and proton conductivity of composite membrane 1@PVA10 is ten times higher than compound 1 at 98% RH and 353 K.

Effect of functionalized SiO 2 toward proton conductivity of composite membranes for PEMFC application

Organic-inorganic composite membranes were prepared by introducing silicon dioxide (SiO2) or functionalized SiO2 (ƒ-SiO2) with various particle sizes into sulfonated poly (arylene ether ketone) (SPAEK) containing pendant groups, and the membrane was manufactured via directly casting which is a cost-competitive method. The structure and morphology of the composite membranes were confirmed by 1H NMR, FT-IR, XRD, and FE-SEM analysis which demonstrated that inorganic nanofillers were successfully introduced. The FE-SEM surface images showed that SiO2 and ƒ-SiO2 particles were very well dispersed within the membrane sheets. The water uptake and swelling ratio of the composite membranes including SiO2 or ƒ-SiO2 almost did not change when compared with the pristine SPAEK membrane. All fabricated membranes demonstrated good thermal/dimensional stabilities, robust mechanical behavior, and excellent proton conductivity. In particular, the SPAEK/ƒ-SiO2 composite membranes exhibited improved ionic conductivity compared with the pristine membrane at 70% relative humidity (RH) due to hydrogen bonding between ─SO3H groups of functionalized inorganic filler and polymer backbone. Furthermore, the maximum power density of SPAEK/ƒ-SiO2 reached as high as 273.11 mW cm−2 at 60°C under 70% RH. Therefore, the composite membranes with ƒ-SiO2 testify to great potential as polymer electrolyte membrane.

Fabrication and Properties of Graphene Oxide/Sulfonated Polyethersulfone Layer-by-layer Assembled Polyester Fiber Composite Proton Exchange Membranes

Using the hydrogen-bonding interaction between graphene oxide(GO) and sulfonated polyethersulfone (SPES), we constructed the multilayer structure of GO and SPES on the polyester fiber mats via layer-by-layer self-assembly. In each self-assembled layer, sulfonic acid groups are arranged along the axis of fiber, which provides the long-range proton transmission channels, promoting the rapidly proton conduction. The performances of the composite membranes based on SPES and multilayer assembled polyester fiber mats were studied. The results show that the proton conductivity of composite membranes increases with the increasing assembly layers. At the same time, the mechanical properties and methanol-resistance of the composite membranes were obviously improved.

The influence of various ionic liquids on the properties of SPEEK membrane doped with mesoporous silica

Anhydrous proton conducting membranes made of different ionic liquids (ILs), sulfonated poly (ether ether ketone) (SPEEK), and mesoporous silica (SiO2) are successfully prepared. Influences of different ionic liquids on the properties of composite membranes doped with 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIm][Tfo]), 1-butyl-3-methylimidazolium chloride ([BMIm]Cl), diethylmethylammonium trifluoromethanesulfonate ([dema][Tfo]), and 1-ethylimidazolium trifluoromethanesulfonate ([EIm][Tfo]) ionic liquids are described. Fourier transform infrared spectroscopy (FT-IR) analysis showed that there were interactions between ionic liquids, SPEEK and mesoporous silica. IL leaching studies demonstrated that IL loss decreased significantly after doping with SiO2. The proton conductivity study showed that both anions and cations of IL influenced the proton conductivity of the composite membranes. Proton conductivity of composite membranes displayed a positive correlation with the number of hopping sites within IL cation structures. Of all the conducting membranes studied, SP/SiO2-7.5/[BMIm][BF4]-50 showed the highest anhydrous proton conducting ability (15mScm−1 at 200°C). Therefore, it is expected to find applications in proton exchange membrane fuel cells under medium temperature, anhydrous conditions.

Anhydrous proton conducting poly(vinyl alcohol) (PVA)/ poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS)/1,2,4-triazole composite membrane

The design and fabrication of anhydrous proton exchange membranes are critically important for high temperature proton exchange membrane fuel cell (HT-PEMFC) operating between 100 and 200 °C. Herein, we demonstrate a novel proton conducting membrane consisting of poly(vinyl alcohol) (PVA), poly (2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) and 1,2,4-triazole, which was fabricated by physical blending, casting and solvent evaporation techniques. The in-situ chemical cross-linking was performed by glutaraldehyde (GA) to improve the water management of the membranes. The molecular structure of the membranes and intermolecular interactions between the constituents were confirmed by Fourier-transform infrared spectroscopy (FT-IR). The surface and cross-section morphologies of the membranes were observed by scanning electron microscopy (SEM). The thermal stability performance of the membranes was studied with thermogravimetric analysis (TGA). In order to determine the physico–chemical properties of the membranes, water uptake (WU), dimensional change and ion exchange capacity (IEC) tests were carried out. The proton conductivities of composite membranes increase with the temperature and the temperature dependencies exhibit an Arrhenius behavior. Proton conductivity measurements revealed an optimum ratio between PAMPS and 1,2,4-triazole content to achieve higher proton conductivity. In anhydrous state at 150 °C, the highest proton conductivity measured was 0.002 S/cm for PVA:PAMPS:1,2,4-triazole (1:1:1) composition. Overall, our investigation showed that 1,2,4-triazole is a promising proton carrier reagent above 100 °C when it is embedded into appropriate host polymers.

Low-swelling proton-conducting multi-layer composite membranes containing polyarylene ether nitrile and sulfonated carbon nanotubes for fuel cells

To overcome the difficulties of excessively swollen or dissolve of sulfonated polyarylene ether nitrile in high temperature, the multi-layer proton exchange composite membranes based on sulfonated polyarylene ether nitrile (SPEN) and sulfonated carbon nanotubes (S-CNTs) were designed via facile step-by-step solution casting technique. The multi-layer structure of membranes can make the membrane more compact and reached the aim of low-swelling. The multi-layer structure of composite membrane was confirmed through scanning electron microscope, exhibiting improved dimensional stability, larger tensile strength and elongation at break than pure SPEN with a certain content of S-CNTs in the wet state. The proton conductivity of composite membranes with 3 wt% S-CNTs achieved 0.094 and 0.275 S/cm at 20 °C and 80 °C, respectively, which is higher than that of Nafion 117. Besides, the methanol permeability of SPEN/S-CNTs/SPEN composite membranes is lower than that of the commercial Nafion 117 membrane. All the data prove that the multi-layer composite membranes may be potential proton exchange membrane for fuel cells applications.

The Effect of Nano-Morphology Modification Using an Amphiphilic Polymer on the Proton Conductivity of Composite Membrane for a Polymer Membrane-Based Fuel Cell.

The effect of morphology modification using an amphiphilic polymer on the proton conductivity of composite membrane for a polymer membrane-based fuel cell was investigated. The proton conductivity of each composite membrane was analyzed by the electrochemical impedance spectroscopy (EIS). The morphological change was confirmed by scanning electron microscope (SEM). In the composite membrane, the proton conductive component was sulfonated poly(ether ether ketone) (sPEEK), while the nonconductive component was poly(vinylidenedifluoride) and the amphiphilic polymer as a compatibilizer was urethane acrylate non-ionomer (UAN). UAN as a compatibilizer improved the interfacial stability between sPEEK and PVdF polymers, even though two polymers were apparently immiscible. The homogeneous distribution of sPEEK and PVdF domains in the composite membrane was obtained with the introduction of UAN due to the amphiphilicity. Therefore, it was found that the proton conductivity of the composite membrane increased with the incorporation of UAN as a compatibilizer.

Investigation of nanocomposite membranes based on crosslinked poly(vinyl alcohol)–sulfosuccinic acid ester and hexagonal boron nitride

Hexagonal boron nitride (hBN) has received a great deal of attention from the scientific community owing to its distinctive mechanical properties, chemical stability, electrical features, and thermal stability. This work reports the preparation and characterization of novel anhydrous proton-conducting nanocomposite membranes based on poly(vinyl alcohol) (PVA), sulfosuccinic acid (SSA), and hBN. The proton conductivities of composite membranes were examined as a function of hBN composition and temperature. SSA was used as a sulfonating agent to obtain a crosslinked structure. hBN was incorporated into the PVA–SSA matrix as a proton transfer agent and nanofiller additive. The obtained membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), water uptake, methanol permeability, and impedance spectroscopy. The semicrystalline nature of the composites was confirmed by X-ray investigation. The PVA–SSA–15hBN showed a maximum proton conductivity of 0.028 S cm−1 at 150 °C under anhydrous conditions.

Morphology and proton conductivity of composite membranes based on poly(styrene sulfonic acid–maleic anhydride) nanofibers prepared by electrospinning

Non-woven nanofiber mats of poly(styrene sulfonic acid-co-maleic anhydride) (PSSAMA) and poly(vinyl alcohol) (PVA) were prepared by electrospinning using water as solvent. Composite membranes were prepared by casting a poly(methyl methacrylate) (PMMA) chloroform solution over the PSSAMA/PVA nanofibrous mats. Scanning electron microscopy (SEM) showed that these composite membranes are dense structures formed by fibers with average diameter of about 300 nm which acts as composite filler and proton conducting channels. The proton conducting behavior of these membranes were evaluated by impedance spectroscopy in dry atmosphere and in deionized water. The best proton conductivity of this new type of composite electrolyte membrane was 1.67 mS/cm in a dry state, value which is lower than that of commercial Nafion membrane, in the same condition (9.24 mS/cm). Proton conductivity increased with temperature increase, up to 50 °C, when it reached the maximum value.

Preparation and testing of Nafion/titanium dioxide nanocomposite membrane electrode assembly by ultrasonic coating technique

ABSTRACTMembrane electrode assemblies with Nafion/nanosize titanium dioxide (TiO2) composite membranes were manufactured with a novel ultrasonic‐spray technique (UST) and tested in proton exchange membrane fuel cell (PEMFC). The structures of the membranes were investigated by scanning electron microscopy (SEM), X‐ray diffraction (XRD), and thermogravimetric analysis. The composite membranes gained good thermal resistance with insertion of TiO2. The SEM and XRD techniques have proved the uniform and homogeneous distribution of TiO2 and the consequent enhancement of crystalline character of these membranes. The existence of nanometer size TiO2 has improved the thermal resistance, water uptake, and proton conductivity of composite membranes. Gas diffusion electrodes were fabricated by UST. Catalyst loading was 0.4 (mg Pt) cm−2 for both anode and cathode sides. The membranes were tested in a single cell with a 5 cm2 active area operating at the temperature range of 70°C to 110°C and in humidified under 50% relative humidity (RH) conditions. Single PEMFC tests performed at different operating temperatures indicated that Nafion/TiO2 composite membrane is more stable and also performed better than Nafion membranes. The results show that Nafion/TiO2 is a promising membrane material for possible use in PEMFC at higher temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40541.

Sulfonated mesoporous benzene-silica-embedded sulfonated poly(ether ether ketone) membranes for enhanced proton conduction and anti-dehydration

In polymer electrolyte fuel cell operation, a decrease in the proton conductivity of the membrane at reduced humidity is a main cause for poor cell performance at high temperature. To alleviate the dehydration of the membrane at high temperature, sulfonated mesoporous benzene-silica (sMBS) particles are embedded in sulfonated poly(ether ether ketone) (sPEEK) membranes. As the sMBS itself is highly sulfonated on both organic and inorganic moieties, the proton conductivity of composite membranes is much higher than that of the pristine sPEEK membrane, and it reaches that of Nafion 117 at a high relative humidity (RH) of 90%. The dehydration rate of the membrane is reduced significantly by the capillary condensation effect of sMBS particles with the nanometer-scale 2-D hexagonal cylindrical pores, and the proton conductivity of the composite membranes, 0.234 × 10−1 S cm−1, is much higher than that of pristine sPEEK membrane, 0.59 × 10−3 S cm−1, at a relatively low humidity of 40% RH. This maintenance of high conductivity at low humidity is attributed to the high water-holding capacity of the sMBS proton conductors. The sMBS-embedded sPEEK composite membranes show a much lower methanol permeability of 2–5 × 10−7 cm2 s−1 compared to that of Nafion 117, which is 1.6 × 10−6 cm2 s−1 at room temperature.

Morphology and Proton Conductivity of Composite Membranes Based on PWA and PPEK

A series of HPA-containing Poly(phthalazinone ether ketone) (PPEK) membranes was prepared and their microstructure and conductivities were studied in this work. The results showed the composite membrane had no proton conducting ability with PWA content less than 75%, while the conductivity for the PWA/(PEEK-PVP) membranes with 35% of PWA was higher than 4×10-4 S/cm. Proton conductivities up to 4.86×10-3 S/cm have been measured at temperatures up to at 140°Cand 100% RH for PWA/(PEEK-PVP) membranes with 35% of PWA and 70% PVP. The relationship of conductivity and the morphology of the PPEK/PWA membranes showed that the PWA particle dispersion is the key parameters.

Nafion/titanium silicon oxide nanocomposite membranes for PEM fuel cells

In the present study, Nafion/Titanium Silicon Oxide (TiSiO4) nanocomposite membranes were prepared by recasting method for proton exchange membrane fuel cells. The composite membrane containing 10 wt% TiSiO4 had a membrane thickness of 80 µm. The membrane was characterized by thermogravimetric analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). SEM and XRD results have proven the uniform and homogeneous distribution of TiSiO4 in Nafion, and consequently, the crystalline character of these membranes was enhanced. The energy-dispersive X-ray analysis has also indicated uniform distribution of TiSiO4 on the surface of the nanocomposite membrane. The existence of nanometer-size TiSiO4 has improved the thermal resistance, water uptake, and proton conductivity of composite membranes. Single fuel cell tests were performed at different operating temperatures with membrane electrode assemblies prepared by Nafion and Nafion/TiSiO4 nanocomposite membranes. The highest performance was obtained with Nafion/TiSiO4 membrane at 85 °C. These results indicate that Nafion/TiSiO4 composite is a promising membrane material for possible use in proton exchange membrane fuel cells. Copyright © 2012 John Wiley & Sons, Ltd.