Hydrogen production by photocatalytic membranes fabricated by supersonic cluster beam deposition on glass fiber filters

Photoactive membranes coated with TiO₂ and Pt/TiO₂ nanostructured thin films were produced by one-step deposition of gas phase nanoparticles on glass fiber filters. Pt/TiO₂ nanoparticles (0–1.5 wt.% Pt content) were produced by flame spray pyrolysis, starting from liquid solutions of the Ti and Pt precursors, and then expanded in a supersonic beam to be deposited on the filters. The nanostructured coatings were composed of crystalline nanoparticles (mainly anatase phase), without any need of post-deposition annealing. The so obtained photocatalytic membranes were tested in hydrogen production by photo-steam reforming of ethanol in an expressly set-up diffusive photoreactor. The reaction rate was found to increase with increasing the Pt content in the photoactive material, up to 1.5 wt.% Pt. The use of these membranes allowed a significant increase of the hydrogen production rate compared to that obtained with the same photoactive Pt/TiO₂ films deposited on a quartz substrate.     

BaCe0.85Tb0.05Co0.1O3−δ perovskite hollow fibre membranes for hydrogen/oxygen permeation

Co-doped BaCe_0.85Tb_0.05Co_0.1O_3−δ (BCTCo) nanopowder was synthesized via a sol–gel method using ethylenediaminetetraacetic acid (EDTA) and citric acid as the chelating agents. Using the resultant powder, BCTCo perovskite hollow fibre membranes were then fabricated by the combined phase inversion and sintering technique. Properties of the BCTCo powder and the hollow fibre membranes in terms of crystalline phase, morphology, electrical conductivity, porosity, mechanical strength and hydrogen/oxygen permeation were investigated by a variety of characterization methods. The results indicated that doping of cobalt in the BCTb oxide led to a higher electrical conductivity and lower calcination temperature for the powder precursor to a perovskite structure as well as sintering temperature for the hollow fibre precursors to gastight membranes. In order to obtain gastight and robust hollow fibre membranes, the sintering temperature should be controlled between 1300 and 1450 °C. The maximum hydrogen flux through the BCTCo hollow fibre membranes reached up to 0.385 mL cm⁻² min⁻¹ at 1000 °C under 50% H₂–He/N₂ gradient, which is higher than that of the un-doped BCTb hollow fibre membranes with the same effective thickness, and especially much higher than that obtained from other proton conductors due to the asymmetric structure of the membrane designed. Moreover, the BCTCo hollow fibre membrane also exhibited noticeable oxygen permeation fluxes, i.e. 0.122 mL cm⁻² min⁻¹ at 1000 °C under the air/He gradient. However, doping of cobalt might damage the mechanical stability of the perovskite membranes in the hydrogen-containing atmosphere.     

Sulfonation of PEEK-WC polymer via chloro-sulfonic acid for potential PEM fuel cell applications

The preparation and characterization of thin dense sulfonated poly-ether-ether-ketone with cardo group (PEEK-WC) membranes for proton exchange membrane fuel cell (PEMFC) applications are described. The sulfonation of PEEK-WC polymer was realized via chloro-sulfonic acid and different kinds of membrane samples were prepared with a sulfonation degree ranging from 67 to 99%. The degree of sulfonation, homogeneity and thickness significantly affect both the membrane transport properties and the electrochemical performances. The dense character of the membranes was confirmed by SEM analysis. Proton conductivity measurements were carried out in a temperature range from 30 to 80 °C and at 100% of relative humidity, reaching 5.40×10⁻³ S/cm⁻¹ as best value at 80 °C and with a sulfonation degree (DS) of 99%. At the same conditions, a water uptake of 17% was achieved. DSC and TGA characterizations were used in order to determine the thermal stability of the membranes, confirming a T_g ranging between 206 and 216 °C depending on the DS, whereas FT-IR yielded indication about intermolecular interactions and water uptake at various sulfonation degrees.     

Characterization of novel GdBa0.5Sr0.5Co2−xFexO5+δ perovskites for application in IT-SOFC cells

Novel, Sr-substituted A-site ordered perovskites with GdBa_0.5Sr_0.5Co_2−xFe_xO_5+δ (0 ≤ x ≤ 2) chemical composition were studied, and results of measurements of their phase composition, crystal structure, oxygen content δ, transport properties and chemical stability in relation to ceria electrolyte are presented in this work. It was found that despite 50% substitution of Ba by Sr, the tendency of ordering in A-sublattice is retained in Co-rich materials, but with the increase of iron content, a significant amount of unordered, but also perovskite phase appears. Compounds with high Co content possess highest electrical conductivity, which for GdBa_0.5Sr_0.5Co₂O_5+δ greatly exceeds 1000 S cm⁻¹ at temperatures above 400 °C. Seebeck coefficient remains positive for all studied compositions in 25–850 °C temperature range, indicating dominance of holes as main charge carriers. The double perovskite structure is responsible for a high deviation from the oxygen stoichiometry in studied materials, which increases considerably above 300 °C.     

Pulsed laser deposition of manganese oxide thin films for supercapacitor applications

Thin films of manganese oxides have been grown by the pulsed laser deposition (PLD) process on silicon wafer and stainless steel substrates at different substrate temperatures and oxygen gas pressures. By proper selection of processing parameters such as temperature and oxygen pressure during the PLD process, pure crystalline phases of Mn₂O₃, Mn₃O₄ as well as amorphous phase of MnO_x were successfully fabricated as identified by X-ray diffraction. The pseudo-capacitance behaviours of these different phases of manganese oxides have also been evaluated by the electrochemical cyclic voltammetry measured in 0.1 M Na₂SO₄ aqueous electrolyte at different scan rates. Their specific current and capacitance determined by electrochemical measurements were compared and the results show that crystalline Mn₂O₃ phase has the highest specific current and capacitance, while the values for crystalline Mn₃O₄ films are the lowest. The specific current and capacitance values of the amorphous MnO_x films are lower than Mn₂O₃ but higher than Mn₃O₄. The specific capacitance of Mn₂O₃ films of 120 nm thick reaches 210 F g⁻¹ at 1 mV s⁻¹ scan rate with excellent stability and cyclic durability. This work has demonstrated that PLD is a very promising technique for screening high performance active materials for supercapacitor applications due to its excellent flexibility and capability of easily controlling chemical composition, microstructures and phases of materials.     

Styrene-co-butyl acrylate copolymers with potential application as membranes in PEM fuel cell

Styrene-butyl acrylate (St-BuA) copolymers were obtained by mass free radical copolymerization reactions, using BPO as initiator. A 70:30 (St-BuA) comonomer composition was selected. Three different molar concentrations of sulfonating agent (50, 100 and 150%) were considered to obtain the sulfonated copolymer (sSt-BuA) and membranes were casted from sSt-BuA copolymers. Copolymers were characterized with FTIR, TGA and NMR ¹H and mechanically by TMA. The sSt-BuA sulfonation degree (SD) effect on the ion-exchange capacity (IEC) was evaluated by titration and water uptake (WU) by gravimetry. Microstructure was also observed using scanning electron microscopy (SEM), and its electrochemical properties were evaluated by electrochemical impedance spectroscopy (EIS). The chemical composition of St-BuA copolymer was confirmed by proton nuclear magnetic resonance (NMR ¹H) spectroscopy. Fourier transformed infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA) analysis also confirmed the existence of both comonomers and a successful sulfonation up to an actual 30% level, as well as a good thermal stability over 300 °C for the molecular structure and over 150 °C for sulfonated membranes. TMA indicate an increase in flexure modulus along degree of sulfonation. SEM images show a highly dense material with low pore size for the sulfonated copolymer. The IEC values obtained varied from 0.83 to 1.18 meq g⁻¹, depending on sulfonation degree. The proton conductivity for St-BuA 50% membrane (9.77 × 10⁻⁵ S cm⁻¹) was a two order of magnitude lower than the commercial Nafion membrane (4.53 × 10⁻³ S cm⁻¹). Thermal, mechanical and electrochemical results demonstrate that these sSt:BuA copolymers are promising materials to be used as membranes in fuel cells applications.     

I-V characteristics of a-Si-c-Si hetero-junction diodes made by hot wire CVD

p-Type hydrogenated amorphous silicon (a-Si:H) was deposited on n-type crystalline silicon (c-Si) substrates to obtain hetero-junction diodes. Additionally, a thin intrinsic a-Si:H layer was inserted between both the p-type film and the n-type substrate to study its passivation effect on the c-Si surface. The amorphous films were obtained by the hot wire chemical vapor deposition (HWCVD) technique, using a tungsten filament and silane (SiH₄), hydrogen (H₂) and diborane (B₂H₆) gases, where the deposition parameters such as gas flow, substrate temperature and filament temperature were varied. Optical band gap, deposition rate and conductivity were measured for all the films. We studied the influence of the quality of the amorphous films upon the performance of the hetero-junction diodes. In particular, the diode ideality factor (n) and the saturation current density (J₀) were determined by measuring the current-voltage characteristics in dark conditions. It is shown that the presence of the intrinsic layer is fundamental for making good diodes, since devices made without this film cause the diodes to have high saturation current density and ideality factor (J₀>10×10⁻⁶ A/cm², n>4) as compared to diodes with a good intrinsic layer (J₀=5×10⁻⁹ A/cm², n=1.39). The results obtained are encouraging, but the quality of the intrinsic films still should be improved for applying them to HIT solar cells.     

Chemical and radiation crosslinked polymer electrolyte membranes prepared from radiation-grafted ETFE films for DMFC applications

To develop a highly chemically stable polymer electrolyte membrane for application in a direct methanol fuel cell (DMFC), doubly crosslinked membranes were prepared by chemical crosslinking using bifunctional monomers, such as divinylbenzene (DVB) and bis(p,p-vinyl phenyl) ethane (BVPE), and by radiation crosslinking. The membranes were prepared by grafting of m,p-methylstyrene (MeSt) and p-tert-butylstyrene (tBuSt) into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent sulfonation. The effects of the DVB and BVPE crosslinkers on the grafting kinetics and the properties of the prepared membranes, such as water uptake, proton conductivity and chemical stability were investigated. Radiation crosslinking was introduced by irradiation of the ETFE base film, the grafted film or the sulfonated membrane. The membrane crosslinked by DVB and BVPE crosslinkers and post-crosslinked by γ-ray irradiation of the corresponding grafted film possessed the highest chemical stability among the prepared membranes, a significantly lower methanol permeability compared to Nafion^® membranes, and a better DMFC performance for high methanol feed concentration. Therefore, this doubly crosslinked membrane was promising for application in a DMFC where relatively high methanol concentration could be fed.     

Optical, structural and photoelectron spectroscopic studies on amorphous and crystalline molybdenum oxide thin films

Optical, structural and electronic properties of amorphous and crystalline molybdenum oxide thin films have been investigated. As-deposited amorphous films got crystallized into a layered orthorhombic phase on annealing at 350°C. Refractive index (n) and extinction coefficient (k) of as-deposited films and films annealed at 150°C, 240°C and 350°C have been calculated using reflectance and transmittance data. Spectral dependence of absorption coefficient has been explained on the basis of charge transfer transition mechanism. Optical band gap of amorphous MoO_3−x is 3.16 eV and it has increased by 0.11 eV on crystallization. XPS core level analysis reveals the presence of Mo⁺⁴, Mo⁺⁵ and Mo⁺⁵ oxidation states in amorphous films, proving oxygen deficiency in as-deposited films. Same studies on crystalline films show the presence of only Mo⁺⁶ states. Valence band spectrum of amorphous films reveal emission from Mo4d levels, which is absent in crystalline films. Complete correlation is seen between the optical properties and XPS data.     

Preparation and characterization of sulfonated PEEK-WC membranes for fuel cell applications: A comparison between polymeric and composite membranes

Sulfonated poly(etheretherketone) with a cardo group (SPEEK-WC) exhibiting a wide range of degree of sulfonation (DS) was used to prepare polymeric membranes and composite membranes obtained by incorporation of an amorphous zirconium phosphate sulfophenylenphosphonate (Zr(HPO₄)(O₃PC₆H₄SO₃H), hereafter Zr(SPP)) in a SPEEK-WC matrix. The nominal composition of the composite membranes was fixed at 20 wt% of Zr(SPP). Both types of membrane were characterized for their proton conductivity, methanol permeability, water and/or methanol uptake, morphology by SEM and mechanical properties. For comparison, a commercial Nafion 117 membrane was characterized under the same operative conditions. The composite membranes exhibited a reduced water uptake in comparison with the polymeric membranes especially at high DS values and temperature higher than 50 °C. As a result, the water uptake into composite membranes remained about constant in the range 20–70 °C. The methanol permeability (P) of both polymeric and composite membranes was always lower than that of a commercial Nafion 117 membrane. At 22 °C and 100% relative humidity (RH), the proton conductivities (σ) of the polymeric membranes increased from 6 × 10⁻⁴ to 1 × 10⁻² S cm⁻¹ with the increase of DS from 0.1 to 1.04. The higher conductivity value was comparable with that of Nafion 117 membrane (3 × 10⁻² S cm⁻¹) measured under the same operative conditions. The conductivities of the composite membranes are close to that of the corresponding polymeric membranes, but they are affected to a lesser extent by the polymer DS. The maximum value of the σ/P ratio (about 7 × 10⁴ at 25 °C) was found for the composite membrane with DS = 0.2 and was 2.5 times higher than the corresponding value of the Nafion membrane.     

Synthesis of highly conductive boron-doped p-type hydrogenated microcrystalline silicon (μc-Si:H) by a hot-wire chemical vapor deposition (HWCVD) technique

Boron-doped hydrogenated microcrystalline silicon (μc-Si:H) films were prepared using hot-wire chemical vapor deposition (HWCVD) technique. Structural, electrical and optical properties of these thin films were systematically studied as a function of B₂H₆ gas (diborane) phase ratio (Variation in B₂H₆ gas phase ratio, dopant gas being diluted in hydrogen, affected the film properties through variation in doping level and hydrogen dilution). Characterization of these films from low angle X-ray diffraction and Raman spectroscopy revealed that the high conductive film consists of mixed phase of microcrystalline silicon embedded in an amorphous network. Even a small increase in hydrogen dilution showed marked effect on film microstructure. At the optimized deposition conditions, films with high dark conductivity (0.08 (Ω cm)⁻¹) with low charge carrier activation energy (0.025 eV) and low optical absorption coefficient with high optical band gap (2.0 eV) were obtained. At these deposition conditions, however, the growth rate was small (6 Å/s) and hydrogen content was large (9 at%).     

Non-isothermal kinetics and in situ SR XRD studies of hydrogen desorption from dihydrides of binary Ti–V alloys

Phase transformations during dynamic dehydrogenation of Ti_1−xV_xH₂ (x = 0.1; 0.2; 0.3) were studied using in situ Synchrotron X-Ray Diffraction (SR XRD) and non-isothermal kinetics experiments. The main dehydrogenation path for γ-Ti_1−xV_xH₂ was found to be γ → δ → β → β_alloy. Body-centred tetragonal δ-hydride was found to be an intermediate phase of the γ → β transformation in Ti_0.8–0.9V_0.1–0.2H₂. TDS, in situ SR XRD and isoconversional kinetics studies showed that hydrogen desorption from Ti_1−xV_xH₂ is composed of simultaneous reactions taking place between 300 and 600 °C. The effective activation energy of hydrogen desorption depends on the vanadium contents and the reaction pathway, increasing from 21 kJ/mol H₂ (γ → δ) to 60–110 kJ/mol H₂ (δ → β).     

Effect of HCl addition on the properties of p-type silicon thin films during hot-wire chemical vapor deposition

The effect of HCl addition on the structural, electrical, and optical properties of p-type silicon films, prepared by hot-wire chemical vapor deposition (HWCVD), was investigated. As the ratio of HCl to SiH₄ increased, the amount of amorphous silicon decreased and the crystalline volume fraction increased in the deposited film. To investigate the effect of HCl addition on the deposition behavior in the initial stage, the transmission electron microscope (TEM) grid membrane was exposed for 10 s using a shutter above the grid membrane during HWCVD and the grid membrane was observed by TEM. When HCl was not added, a continuous film was observed on a grid membrane, consisting of crystalline nanoparticles embedded in an amorphous matrix whereas when HCl is added, isolated individual crystalline nanoparticles without amorphous silicon were observed. The HCl addition increased the dark conductivity of films by about 3 orders of magnitude but decreased the optical band gap slightly.     

New non-fluoridated hybrid proton exchange membranes based on commercial precursors

New hybrid proton conducting membranes based on sulfonated copolymers of styrene and allyl glycidyl ether using tetraethyl orthosilicate were syntheses. The composition and structure of the copolymers and membranes has been proven by elemental analysis, IR and NMR spectroscopy. Based on quantum chemical calculations a sulfonation mechanism of copolymers was proposed. The characteristics of membranes were evaluated by thermal analysis, dynamic mechanical analysis, electrochemical impedance spectroscopy, water uptake, swelling and ion exchange capacity tests. The hybrid membranes are characterized by high proton conductivity of 4.21 10⁻² S cm⁻¹ (70 °C, 75% RH), activation energy of proton transport (24.5 kJ mol⁻¹), ion-exchange capacity (2.1 mmol g⁻¹), and thermal stability up to 260°С. The hybrid membranes showed water uptake of 6 and 51% at 30 °C and 100 °C, respectively. The suitability of the hybrid membranes toward fuel cell applications was tested through a single cell analysis.     

Interpenetrating network-forming sulfonated poly(vinyl alcohol) proton exchange membranes for direct methanol fuel cell applications

Poly (vinyl alcohol) was sulfonated and subsequently cross-linked by a thermal curing reaction with dual cross-linkers to prepare membranes for direct methanol fuel cells. Sulfonated poly (vinyl) alcohol (SPVA) with a high degree of sulfonation was synthesized from 4-Formylbenzene-1,3-disulfonic acid disodium salt hydrate via an acetalization reaction with PVA. Various masses of the cross-linking agents 1,3-bis(3-glycidyloxypropyl) tetramethyldisiloxane and 4,4′-oxydiphthalic anhydride were polymerized with SPVA to facilitate manipulation of the properties of the membranes. Notably, the SPVA3 showed excellent proton conductivity (cf. σ  = 0.218 S cm⁻¹ at 70 °C and Nafion 117 = 0.127 S cm⁻¹), and low methanol permeability (around one half of that Nafion 117). These results suggest that the cross-linked SPVA membranes hold promise as potential proton exchange membranes and given their high proton conductivity and low methanol permeability they may offer advantages when used in direct methanol fuel cells (DMFCs) applications.     

Cross-linked, ETFE-derived and radiation grafted membranes for anion exchange membrane fuel cell applications

To develop a series of cross-linked anion exchange membranes for application in fuel cells, poly(ethylene-co-tetrafluoroethylene) (ETFE) films was radiation grafted with vinyl benzyl chloride (VBC), followed by quaternization and crosslinking with 1,4-Diazabicyclo[2,2,2]octane (DABCO), alkylation with p-Xylylenedichloride (DCX), and quaternization again with trimethylamine (TMA). These anion exchange membranes were characterized in terms of water uptake, ion-exchange capacity, ionic conductivity as well as thermal stability. The chemical structures of the membranes were examined by FT-IR. The anion conductivity of the resulting alkaline anion exchange membrane is as high as 0.039 S cm⁻¹ at 30 °C in deionized water and the ionic conductivity increases with the increasing of temperature from 20 to 80 °C. The membrane is stable after being treated by 10 M potassium hydroxide solution at 60 °C for 120 h .The fuel cell performance with the final AAEM obtained in a H₂/O₂ single fuel cell at 40 °C with this AAEM was 48 mW cm⁻² at a current density of 69 mA cm⁻².     

Mechanochemical processing of BaZr1−yYyO3−δ (y = 0.15, 0.20) protonic ceramic electrolytes: Phase purity,microstructure, electrical properties and comparison with other preparation routes

BaZrO₃-based materials have been intensively researched due to their potential application as high-temperature proton conductors in devices such as proton ceramic fuel cells (PCFCs), separation membranes and electrolysers. Nonetheless, their implementation in these devices has often been constrained due to their processing difficulties, namely the formation of Ba-deficient compositions, coexistence of separate perovskite phases or the formation of segregated phases of the acceptor dopant. In this context, the current article shows mechanosynthesis to be an efficient preparation method for Ba(Zr,Y)O_3-δ materials, producing pure powders, containing nanometric crystallites, that offer good densification and grain growth. The phase formation, microstructure and electrical properties of the most promising BaZr_1-yY_yO_3-δ compositions, with yttrium contents of y = 0.15 (BZY15) and y = 0.20 (BZY20) are investigated and compared with literature data of materials made by other processing routes. Such a comparison highlights that phase separation of such compositions, commonly reported in the literature, does not occur for these mechanosynthesised materials of high homogeneity. Furthermore, high electrical performances can be obtained by this technique that can compete with some of the best reported in the literature. Electrical conductivity as a function of both oxygen and water partial pressure, in the temperature range of 550 °C ? 850 °C, are measured for both compositions and the partial conductivities of protons, oxygen vacancies and electron holes are determined from the defect model. The electron-hole conductivity of BZY20 is observed to be higher than that of BZY15 under all conditions, while proton and oxide-ion conductivities are shown to be higher for the composition BZY15.     

Effects of tritium content on lattice parameter, 3He retention,and structural evolution during aging of titanium tritide

Effects of tritium content on crystal lattice, ³He retention and structure evolution during aging of Ti tritides were investigated using X-ray diffraction, together with analysis of ³He release. Phase transformation and lattice parameters of the Ti tritides varied apparently depending on tritium stoichiometry. Initial tritium content in the Ti tritides showed significant effects on ³He retention due to the existence of α + δ phase boundaries and lattice symmetry in the Ti tritide. The critical contents of ³He release in the α + δ phase region and ε phase region were found to be smaller than that in the δ phase region. Variation of crystal lattice structures of α + δ, δ and ε phases in the Ti tritides has been investigated, and evolution of ³He during aging is mainly governed by the finite defects of self-interstitial atoms, dislocation loops, ³He bubbles, and dislocations created by formation and growth of ³He bubbles. In the α + δ two phase region, the phase boundaries played an important role to accumulate ³He bubbles and cause inter-bubble fracture. In the ε phase region, a preferred condensation of finite defects in basal plane of Ti tritide lattice and formation of a dislocation network were identified.     

Synthesis and characterization of BaIn0.3−xYxCe0.7O3−δ (x = 0, 0.1, 0.2, 0.3) proton conductors

The morphological and electrical properties of yttrium (Y) and indium (In) doped barium cerate perovskites of the form BaIn_0.3−xY_xCe_0.7O_3−δ (with x = 0–0.3) prepared by a modified Pechini method were investigated as potential high temperature proton conductors with improved chemical stability and conductivity. The sinterability increased with the increase of In-doping, and the perovskite phase was found in the BaIn_0.3−xY_xCe_0.7O_3−δ solid solutions over the range 0 ≤ x ≤ 0.3. The conductivities decreased from x = 0.3 to 0 while the tolerance to wet CO₂ improved for BaIn_0.3−xY_xCe_0.7O_3−δ samples with an increase of In-doping. BaIn_0.1Y_0.2Ce_0.7O_3−δ was found to have relatively high conductivity as well as acceptable wet CO₂ stability.     

Effect of cesium salt of tungstophosphoric acid (Cs-TPA) on the properties of sulfonated polyether ether ketone (SPEEK) composite membranes for fuel cell applications

We have prepared composite membranes for fuel cell applications. Cesium salt of tungstophosphoric acid (Cs-TPA) particles was synthesized by aqueous solutions of tungstophosphoric acid and cesium hydroxide and, Cs-TPA particles and sulfonated (polyether ether ketone) (SPEEK) with two sulfonation degrees (DS), 60 and 70%have been used. We examined both the effects of Cs-TPA in SPEEK membranes as functions of sulfonation degrees of SPEEK and the content of Cs-TPA. The performance of the composite membranes was evaluated in terms of water uptake, ion exchange capacity, proton conductivity, chemical stability, hydrolytic stability, thermal stability and methanol permeability. The morphology of the membranes was investigated with SEM micrographs. Increasing sulfonation degree of SPEEK from 60 to 70 caused agglomeration of the Cs-TPA particles. The methanol permeability was reduced to 4.7 × 10⁻⁷ cm²/s for SPEEK (DS: 60%)/Cs-TPA membrane with 10 wt.% Cs-TPA concentration, and acceptable proton conductivity of 1.3 × 10⁻¹ S/cm was achieved at 80 °C under 100% RH. The weight loss at 900 °C increased with the addition of inorganic particles, as expected. The hydrolytic stability of the SPEEK/Cs-TPA based composite membranes was improved with the incorporation of the Cs-TPA particles into the matrix. We also noted that SPEEK60/Cs-TPA composite membranes were hydrolytically more stable than SPEEK70/Cs-TPA composite membranes. On the other hand, Methanol, water vapor, and hydrogen permeability values of SPEEK60 composite membranes were found to be lower than that of Nafion^®.