Highly conductive proton exchange membranes based on sulfonated poly(phthalazinone ether sulfone) and cerium sulfophenyl phosphate

Polymer composite membranes based on sulfonated poly(phthalazinone ether sulfone) (SPPES) and cerium sulfophenyl phosphate (CeSPP) are prepared. Three CeSPP concentrations are used: 10, 20, and 30 wt.%. The membranes are characterised by infrared spectroscopy (IR), X-ray diffraction spectroscopy, thermal gravimetric analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The IR results indicate the formation of intense hydrogen bonds between CeSPP and SPPES molecules. The SEM micrographs show that CeSPP well dispersed in composite membrane. The properties of the membranes are evaluated by their water uptake, ionic exchange capacity, proton conductivity and methanol permeability. The proton conductivity of the SPPES (DS 91%)/CeSPP (30 wt.%) composite membrane (I) reaches 0.384 S/cm at 130 °C and 100% relative humidity, which is three times more than Nafion®117. CeSPP improves the conductivity of composite membranes at a low humidity. At 105 °C and 70% RH, the proton conductivity of membrane (I) is 9.1 × 10⁻² S/cm, while Nafion®117 8.8 × 10⁻³ S/cm. The methanol permeability of membrane (I) is 10⁻⁸ cm²/s. That is much lower than Nafion®117.     

Sulfonated poly(arylene ether sulfone)/Laponite-SO3H composite membrane for direct methanol fuel cell

Polymer nanocomposite membranes based on sulfonated poly(arylene ether sulfonate) (SPAES) containing a flake filler (Laponite) with varying degrees of sulfonation, were prepared and characterized for application in direct methanol fuel cells (DMFCs). Unlike most other clays, Laponite crystals are very small in size with a very low aspect ratio (diameter to thickness ratio) of 25–30. They improve the mechanical, thermal properties and decreased the fuel permeability. However, polymer composite membranes containing non-proton conducting inorganic particles tend to show low proton conductivity, as compared with pristine polymer membranes. To resolve this problem, prior to the preparation of the composite membranes, Laponite-Na+(NLa) was sulfonated with various amounts of organo silanes (3-Mercaptopropyl trimethoxysilane (SH-silane)) via an ion exchange method. Functionalized Laponite with the organic silane compound showed higher ion exchange capacity and ion conductivity, respectively. In order to minimize the loss of proton conductivity while reducing the methanol permeability, various amounts (0.5–2.0 wt%) of the organically sulfonated Laponite (SLa) were introduced into the SPAES matrices. The performances of hybrid membranes for DMFCs in terms of mechanical properties, behavior of water in membranes, proton conductivity and methanol permeability were investigated.     

UV curable sulfonated hybrid materials and their performance as proton exchange membranes

In this study 2-acrylamido-2-methylpropanesulfonic acid (AMPS) containing UV curable nanocomposite membranes were prepared by using the sol–gel method. Tetraethylorthosilicate (TEOS), and 3-(methacryloyloxy)propyl trimethoxysilane (MAPTMS) were used, respectively as an inorganic precursor and coupling agent. Cross linking agents such as poly(ethylene glycol diacrylate) (PEGMA) and ethylene glycol dimethacrylate (EGDMA) were used to arrange the mechanical and physical properties of the resulting hybrid membrane. The hybrid formulation polymerized under UV irradiation and the gel percentage, water uptake of the membranes were calculated. The polymerization conversion of the organic part was investigated by using photo-differential scanning calorimetry (photo-DSC). The thermal and mechanical properties of the membranes indicated good stability. The morphological structure of membranes was investigated by scanning electron microscopy (SEM). In addition proton conductivity and methanol selectivity measurements were performed. The proton conductivity of the AMPS20–SOLGEL30 nanocomposite membrane is about 0.138 S cm^?1 at 50 °C. Selectivity toward methanol for the same membrane is very low with a selectivity factor of α = 0.032, which satisfies the requirements for DMFC applications.     

Nanoporous anatase ceramic membranes as fast-proton-conducting materials

Nanoporous anatase ceramic membranes were prepared via particulate sol–gel processes. The calcined xerogels were mesoporous, with a BET surface area of 121 m²/g, an average pore diameter of 5.8 nm and a pore volume of 0.236 cm³/g. Proton conductivity of the membranes was measured as a function of temperature and relative humidity, R.H. When anatase membranes are treated at pH 1.5, the proton conductivity increased in the whole range of temperature and R.H. It indicates that the surface site density (number of water molecules per square nanometer) of these materials has a strong effect on conductivity. The proton conductivity of the studied anatase membranes followed an Arrhenius-like dependence on the temperature (from room temperature to 90 °C), in both treated and untreated membranes. A sigmoidal dependence of the conductivity on the R.H. was observed with the greatest increase noted between 58 and 81% R.H. in both treated and untreated anatase membranes. The highest value of proton conductivity was found to be 0.015 S/cm at 90 °C and 81% R.H., for treated anatase ceramic membranes. An increase of the conductivity could be achieved by means of longer times of treatment.According to the activation energy values, proton migration in this kind of materials could be dominated by the Grotthuss mechanism in the whole range of R.H. The similar values of proton conductivity, lower cost and higher hydrophilicity of these membranes make them potential substitutes for perfluorosulfonic polymeric membranes in proton exchange membrane fuel cells (PEMFCs).     

Non-fluorinated hybrid composite membranes based on polyethylene glycol functionalized polyhedral oligomeric silsesquioxane [PPOSS] and sulfonated poly(ether ether ketone) [SPEEK] for fuel cell applications

Novel hybrid composite membranes were prepared by blending poly(ethylene glycol) functionalized polyhedral oligomeric silsesquioxane [PPOSS] as nanofiller in varying concentration ranging from 1 to 5% (w/w) into sulfonated poly(ether ether ketone) [SPEEK] with degree of sulfonation ～55% for proton exchange membrane fuel cells [PEMFCs]. The effect of incorporation of PPOSS into SPEEK matrix was investigated in terms of thermomechanical and morphological properties, water uptake and proton conductivity of SPEEK. All the composite membranes were thermally and mechanically stable up to 250 °C. Transmission electron microscopy (TEM) revealed that the smallest particle size (～100 nm) of PPOSS was found for SPEEK membranes containing 2% (w/w) PPOSS where as agglomeration (～300 nm) was observed at higher loadings of PPOSS. The proton conductivity was found to be dependent on the morphology and was independent of the amount of water present in the membranes. At 100 °C and 100% RH, the highest proton conductivity (47 mS/cm compared 34 mS/cm for neat SPEEK i.e. an increase of ～51%) was recorded at 2% (w/w) PPOSS contents followed by a decrease on further addition of PPOSS.The water uptake of composite membranes increased with concentration of PPOSS while maintaining their hydrolytic stability at 100 °C for more than 24 h.     

Enhancing polymer/graphene oxide gas barrier film properties by introducing new crystals

A transparent, gas barrier film comprised of poly(vinyl alcohol) (PVA) and graphene oxide (GO) is synthesized through combined methods of solution blending and isothermal recrystallization. The recrystallized PVA/GO film with only 0.07 vol% GO gives an O₂ transmission rate <0.005 cc m⁻² day⁻¹ and an O₂ permeability <5.0 × 10⁻²⁰ cm³ cm cm⁻² Pa⁻¹ s⁻¹; hence, it is far superior to other blend polymer/inorganic composites. The excellent O₂ barrier properties are attributed to a unique hybrid of PVA crystals and GO sheets. PVA crystals form around the GO during isothermal recrystallization, indicating that a GO sheet can act as a nucleating agent. The newly formed PVA crystals fill in the spaces between the GO sheets, and together they become ultra-large impermeable regions, which can prevent the passage of O₂. The hybrid film has potential applications in flexible electronics, pharmaceuticals, and food packaging.     

Preparation of high styrenic sulfonated polySEPS/clay composite film for proton exchange membranes (PEMs)

High styrenic sulfonated polystyrene-block-poly(ethyl-ran-propylene)-block-polystyrene (S-polySEPS) containing 65% styrene groups was prepared by sulfonation at the phenyl group. Also, S-polySEPS/clay composite film was produced by mixing organic clay with S-polySEPS in organic blending solvent (THF/DCE/IPA). The proton conductivity of the pure S-polySEPS film and S-polySEPS/clay composite films was ranged from 10^?2 to 10^?1 S cm^?1. In particular, the S-polySEPS/clay 1 wt% composite film was shown higher proton conductivity, higher ion exchange capacity (IEC) and lower water uptake than Nafion^® 117 membrane. However, the proton conductivity of the S-polyseps/clay composite films slightly was decreased with increasing the contents of organic clay. Thermogravimetric analysis (TGA) was carried out to investigate the thermal stability of S-polySEPS/clay composite films. The ¹H NMR and FT-IR analysis is used to verify the sulfonation reaction on the phenyl groups of S-polySEPS. The micro-phase separated images and dispersed organic clay state of the prepared films were confirmed by transmission electron microscopy (TEM) and X-ray diffraction (XRD).     

Anhydrous proton-conducting glass membranes doped with ionic liquid for intermediate-temperature fuel cells

Proton-conducting glass membranes based on SiO₂ monoliths and a protic ionic liquid (diethylmethylammonium trifluoromethanesulfonate, [dema][TfO]) as the anhydrous proton conductor were studied. The [dema][TfO]/SiO₂ hybrid glass membranes were prepared via a sol–gel process. The stability and ionic conductivity of the glass membrane were investigated. The [dema][TfO]/SiO₂ hybrid glass monoliths exhibit very high anhydrous ionic conductivities that exceed 10^?2 S cm^?1 at 120–220 °C.     

Preparation and characterization of low-cost ceramic microfiltration membranes for the removal of chromate from aqueous solutions

Low-cost ceramic microfiltration membranes were prepared using clay of IIT Guwahati. Two membranes were prepared by paste casting followed by sintering at different temperatures, the first one from clay only (membrane A) and the second one from clay with small amounts of sodium carbonate, sodium metasilicate and boric acid (membrane B). Both the membranes were characterized by TGA, SEM, XRD, water permeability test and acid–base treatment. With the increase of sintering temperature, pore size as well as permeability and flexural strength were increasing while porosity and pore density were decreasing. The overall performance of membrane B was better than membrane A. The average pore size, porosity, pore density and flexural strength of membrane B sintered at 1000 °C were 4.58 μm, 0.42, 2.06 × 10¹⁰ m^− 2 and 11.55 MPa respectively. This membrane was used for the removal of chromate from aqueous solutions by micellar enhanced microfiltration (MEMF) using cetylpyridinium chloride (CPC). 100% rejection of chromate ions were obtained at a feed ratio (CPC/chromate) of 10. Based on raw material prices, the membrane cost was estimated to be $19/m². The prepared low-cost membrane showed good promise for the treatment of wastewater containing such heavy metals.     

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).     

CO2-tolerant Ni-La5.5WO11.25-δ dual-phase membranes with enhanced H2 permeability

Enhancing the ambi-polar conductivity of the ceramic hydrogen permeable membrane by introducing an electron conductive metallic phase is quite effective, which is helpful for the hydrogen permeation flux improvement. To develop CO₂-tolerant hydrogen permeable membranes with better hydrogen permeability, Ni-La_5.5WO_11.25-δ (Ni-LWO) cermet membranes are fabricated. The alkaline earth metal-free ceramic LWO is used as the main proton-conductive phase and Ni is used as the main electron-conductive phase. The Ni-LWO membrane exhibits good chemical stability in CO₂-containing atmosphere since its hydrogen permeability maintains well in the measurement for about 180 h. Compared with the LWO ceramic membrane, the hydrogen permeability of the Ni-LWO membrane has been improved significantly. The Ni/LWO ratio has great impact on the performance of the cermet membrane. Meanwhile, among all the dual-phase Ni-LWO membranes with different Ni/LWO volume ratios, the membrane with 60 vol% Ni shows the highest hydrogen permeation flux of 0.18 ml min⁻¹ cm⁻² at 1000 °C when the feed gas contains 50% H₂.     

Improved proton conductivity and methanol permeability of PVA-based proton exchange membranes using diphenylamine-4-sulfonic acid sodium salt and silica nanoparticles

ABSTRACT

A novel series of PVA/DPA-4-SASS/SiO₂ composite membranes were fabricated and characterized in the present study. Compared to the neat PVA, water uptake, proton conductivity, and ion exchange capacity of the membranes were enhanced. The membrane containing 5 Wt. % of SiO₂ nanoparticles and 80 Wt. % of the DPA-4-SASS showed the highest values of water uptake, proton conductivity (1.5 × 10^?1 S/cm) and ion exchange capacity (1.47 mmol/g). The results also indicated that methanol permeability was decreased by increasing the DPA-4-SASS content in the hybrid membranes. Thermal stability and mechanical properties of the cross-linked membranes were also improved.     

Poly(vinyl alcohol)–polyacrylamide blends with cesium salts of heteropolyacid as a polymer electrolyte for direct methanol fuel cell applications

A class of inorganic–organic hybrid membranes with low methanol permeability characteristics for possible direct methanol fuel cell (DMFC) applications was architected, formulated, and fabricated through the blending of poly(vinyl alcohol) (PVA) and polyacrylamide (PAM) followed by crosslinking with glutaraldehyde (Glu). Cesium salts of different heteropolyacids, including phosphomolybdic acid (PMA), phosphotungstic acid (PWA), and silicotungstic acid (SWA), were incorporated into the polymer network to form corresponding hybrid membrane materials, namely, PVA–PAM–CsPMA–Glu, PVA–PAM–CsPWA–Glu, and PVA–PAM–CsSWA–Glu, respectively (where “Cs” together with a heteropolyacid abbreviation indicates the cesium salt of that acid). All the three hybrid polymer membranes fabricated exhibited excellent swelling, thermal, oxidative, and additive stability properties with desired proton conductivities in the range 10^?2 S/cm at 50% relative humidity. A dense network formation was achieved through the blending of PVA and PAM and by crosslinking with Glu, which led to an order of magnitude decrease in the methanol permeability compared to the state‐of‐the‐art commercial Nafion 115 membrane. The hybrid membrane containing CsSWA exhibited a very low methanol permeability (1.4 × 10^?8 cm²/s) compared to other membranes containing cesium salt of heteropolyacids such as PMA and PWA. The feasibility of these hybrid membranes as proton‐conducting electrolytes in DMFC was investigated, and the preliminary results were compared with those of Nafion 115. The results illustrate the attractive features and suitability of the fabricated hybrid membranes as an electrolyte for DMFC applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of a nigerian mesoporous clay-based membrane for uranium removal from underground water

This study reports the removal of uranium in underground wastewater using a Nigerian clay-based membrane. The clay and sintered clay were characterized using XRD, XRF, TGA/DTA, FESEM and PSD. The raw clay was mixed with cassava starch (10, 15, 20 and 25 wt%) and sintered at a temperature of 1300 °C. A multi-point BET analysis of the produced clay-based membranes was conducted to determine the surface area, pore volume and average pore size. Sintering characteristics were determined by apparent porosity, bulk density and flexural strength. The radioactivity of the feed and the permeated water was counted using a gamma spectrometer with an HPGe detector. From the XRD, TGA and FESEM, 1300 °C was found to be optimum for the mullite formation from the clay. The average pore sizes of the produced membranes from the BET results were observed to be in the range from 51 to 70 Å and with a steady state flux range of the tested membranes in the range 1.92×10⁻⁵–2.09×10⁻⁴ m³ m⁻² s⁻¹. The permeation flux produced is of high quality with a rejection in the range of 1.78–2.56 Bq/l of the uranium activity by the tested membranes. This low-cost membrane will have an application for the treatment of uranium-containing wastewater from fracking, oil exploration and phosphate mining industries.     

Study of pervaporation for dehydration of caprolactam through PVA/nano silica composite membranes

We investigated nano silica/PVA composite membranes to propose an improved caprolactam pervaporation (PV) dehydration process. The membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and contact angle measurement. Compared with the pure PVA membranes, the nano silica/PVA composite membranes showed different surface morphologies with enhanced hydrophilicity because of their unique formation. To evaluate PV performance and mechanism, we assessed the permeation flux, separation factor, diffusivity/sorptivity selectivity, and activation energy of the composite membranes. The evaluated results indicate that the nano silica/PVA composite membranes induced a breakthrough in the dehydration of a caprolactam-water mixture with a maximum flux of 3.8 kg m^? 2 h^? 1 and an acceptable separation factor of 150.     

Porous membrane based on chitosan–SiO2 for coin cell proton battery

Porous chitosan–SiO₂ membranes were prepared by ultrasonic mixing solution-cast and porogen removal method at different SiO₂ weight ratios. To remove SiO₂ from chitosan membranes, NaOH solution was used to dissolve SiO₂. Porous chitosan:SiO₂ membrane with the weight ratio 1:2 produced optimum average pore size (8.5 μm) with an amorphous structure and the highest water uptake (257.1%). Further soaking of this membrane in NH₄CH₃COO electrolyte solution for two days produced the highest conductivity (3.6×10⁻³ S cm⁻¹) and optimum breakdown voltage (1.8 V). Fabrication of coin cell proton battery displayed an open circuit potential of 1.5 V for 7 days, maximum power density (6.7 mW cm⁻²) and small current resistance (0.03 Ω). The specific discharge capacities obtained from discharge profile of 39.7 mA h g⁻¹ (0.5 mA) and 43.8 mA h g⁻¹ (1.0 mA) increased as the discharge currents were increased. These results showed that a porous chitosan–SiO₂ membrane is suitable membrane for the proton batteries.     

Design of ceramic filters using Clay/Sawdust composites: Effect of pore network on the hydraulic permeability

Clay based ceramic composite materials with hydraulic permeability were elaborated using sawdust as porogent agent. Their mechanical, morphological, microstructural and pore network properties were investigated. Mixtures in various ratios of two kaolinite clay minerals, Ba (highly plastic) and Va (sand-rich) constitute the five ceramic matrixes studied (CM1, CM2, CM3, CM4 and CM5). Due to their high flexural strength, CM3 and CM4 received 0%, 5%, 10% and 15% sawdust before firing, to improve the porosity of the final matrixes. Results revealed that 900–1000 °C is the range of temperature necessary to get good sintering and flexural strength (≥2 MPa). A typical clay-sawdust based materials (parallepipedic bricks) present porosity ≥40 vol% and 1.5 g/cm³ density. Characterizations such as FTIR, SEM, MIP and flow permeability of ceramic candles were performed. A Hydraulic permeability of ~10 mDarcy was obtained and the mean pore diameter varies from 0.05 to 0.1 µm, in agreement with the microstructure exhibited by the ceramic candles. In the presence of sawdust, pores with size up to 10 µm were observed, justifying the increase of flowing permeability. The elaborated matrixes are promising candidates for microfiltration.     

PWA/silica doped sulfonated poly(ether sulfone) composite membranes for direct methanol fuel cells

A novel sulfonated poly(ether sulfone) (SPES)/phosphotungstic acid (PWA)/silica composite membranes for direct methanol fuel cells (DMFCs) application were prepared. The structure and performance of the obtained membranes were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), water uptake, proton conductivity, and methanol permeability. Compared to a pure SPES membrane, PWA and SiO₂ doped membranes had a higher thermal stability and glass transition temperature (T_g) as revealed by TGA‐FTIR and DSC. The morphology of the composite membranes indicated that SiO₂ and PWA were uniformly distributed throughout the SPES matrix. Proper PWA and silica loadings in the composite membranes showed high proton conductivity and sufficient methanol permeability. The selectivity (the ratio of proton conductivity to methanol permeability) of the SPES‐P‐S 15% composite membrane was almost five times than that of Nafion 112 membrane. This excellent selectivity of SPES/PWA/silica composite membranes indicate a potential feasibility as a promising electrolyte for DMFC. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of ligands of palladium complexes on palladium/Nafion composite membranes for direct methanol fuel cells by supercritical CO2 impregnation method

Palladium/Nafion composite membranes were synthesized by supercritical impregnation method to reduce methanol crossover in direct methanol fuel cells. The palladium complexes used in this study were palladium(II) acetylacetonate, palladium(II) hexafluoroacetylacetonate, and palladium (II) bis(2,2,6,6-tetramethyl-3,5-heptane-dionato). The palladium complexes with various loading amounts from 0.010 to 0.050 g in a high-pressure vessel were dissolved in supercritical CO₂, and impregnated into Nafion membranes.The SEM images indicated that the palladium complexes were successfully deposited into Nafion membrane, and there were no problems such as cracking and pinhole. The EDX analysis showed that the palladium particles were distributed both at the membrane surface and also extended deeper into the membrane. The TEM images indicated that thin dense band of agglomerated Pd particles can be observed near the membrane surface, and a significant number of isolated Pd particles can be seen deeper into the membrane, when Pd(II) acetylacetonate was used as palladium complex. When palladium(II) hexafluoroacetylacetonate and palladium (II) bis(2,2,6,6-tetramethyl-3,5-heptane-dionato) were used, dense band of agglomerated Pd particles cannot be observed near the membrane surface, and small Pd particles were observed inside the membranes.The XRD analysis indicated that the crystalline peak of Nafion membrane at 2θ = 17° increased with the supercritical CO₂ treatment. It means that the degree of crystallinity for Nafion membrane increased by supercritical CO₂. The metal Pd peak at 2θ = 40° was observed for the Pd/Nafion membranes.The methanol crossover was reduced and the DMFC performance was improved for the Pd/Nafion membranes compared with Nafion membrane at 40 °C. The successful preparation of Pd/Nafion membranes by supercritical CO₂ demonstrated an effective alternative way for modifying membranes and for depositing electrode catalytic nanoparticles onto electrolyte.     

New organic–inorganic hybrid membranes based on sulfonated polyimide/aminopropyltriethoxysilane doping with sulfonated mesoporous silica for direct methanol fuel cells

A series of novel composite methanol‐blocking polymer electrolyte membranes based on sulfonated polyimide (SPI) and aminopropyltriethoxysilane (APTES) doping with sulfonated mesoporous silica (S‐mSiO₂) were prepared by the casting procedure. The microstructure and properties of the resulting hybrid membranes were extensively characterized. The crosslinking networks of amino silica phase together with sulfonated mesoporous silica improved the thermal stability of the hybrid membranes to a certain extent in the second decomposition temperature (250–400°C). The composite membranes doping with sulfonated mesoporous silica (SPI/APTES/S‐mSiO₂) displayed superior comprehensive performance to the SPI and SPI/APTES membranes, in which the homogeneously embedded S‐mSiO₂ provided new pathways for proton conduction, rendered more tortuous pathways as well as greater resistance for methanol crossover. The hybrid membrane with 3 wt % S‐mSiO₂ into SPI/APTES‐4 (SPI/A‐4) exhibited the methanol permeability of 4.68 × 10^?6 cm² s^?1at 25°C and proton conductivity of 0.184 S cm^?1 at 80°C and 100%RH, while SPI/A‐4 membrane had the methanol permeability of 5.16 × 10^?6 cm² s^?1 at 25°C and proton conductivity of 0.172 S cm^?1 at 80°C and 100%RH and Nafion 117 exhibited the values of 8.80 × 10^?6 cm² s^?1 and 0.176 S cm^?1 in the same test conditions, respectively. The hybrid membranes were stable up to about 80°C and demonstrated a higher ratio of proton conductivity to methanol permeability than that of Nafion117. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012