Very fast H2 production from the methanolysis of NaBH4 by metal‐free poly(ethylene imine) microgel catalysts

The polyethyleneimine (PEI) microgels prepared via microemulsion polymerization are protonated by hydrochloric acid treatment (p‐PEI) and quaternized (q‐PEI) via modification reaction with methyl iodide and with bromo alkanes of different alkyl chain lengths such as 1‐bromoethane, 1‐bromobutane, 1‐bromohexane, and 1‐bromooctane. The bare p‐PEI and q‐PEI microgels are used as catalysts directly without any metal nanoparticles for the methanolysis reaction of sodium borohydride (NaBH₄). Various parameters such as the protonation/quaternization reaction on PEI microgels, the amount of catalyst, the amount of NaBH₄, and temperature are investigated for their effects on the hydrogen (H₂) production rate. The reaction of self‐methanolysis of NaBH₄ finishes in about 32.5 min, whereas the bare PEI microgel as catalyst finishes the methanolysis of NaBH₄ in 22 min. Surprisingly, it is found that when the protonated PEI microgels are used as catalyst, the same methanolysis of NaBH₄ is finished in 1.5 min. The highest H₂ generation rate value is observed for protonated PEI microgels (10 mg) with 8013 mL of H₂/(g of catalyst.min) for the methanolysis of NaBH₄. Moreover, activation parameters are also calculated with activation energy value of 23.7 kJ/mol, enthalpy 20.9 kJ/mol, and entropy ?158 J/K.mol. Copyright © 2016 John Wiley & Sons, Ltd.     

Poly(acrylic acid)-modified silica nanoparticles as a nonmetal catalyst for NaBH4 methanolysis

In the present work, a SiO₂@PAA catalyst for NaBH₄ methanolysis composed of silica nanoparticles modified with poly(acrylic acid) has been developed. The morphology and composition of the prepared SiO₂@PAA catalyst were analyzed with transmission electron microscopy, Fourier transform-infrared spectroscopy, x-ray photoelectron spectroscopy and thermogravimetric analysis. This catalyst showed excellent catalytic performance for methanolysis of NaBH₄. The NaBH₄ methanolysis reaction catalyzed by SiO₂@PAA showed an average hydrogen generation rate 5.5 times as high as the reaction catalyzed by unmodified SiO₂ and 10.6 times as high as the uncatalyzed reaction, respectively. The activation energy for methanolysis of NaBH₄ catalyzed by this SiO₂@PAA catalyst was 24.03 kJ/mol. Moreover, although the catalytic activity of SiO₂@PAA catalyst partially lost after being used, it could be restored after being regenerated by washing with diluted hydrochloric acid solution.     

Effective TiO2 supported Cu-Complex catalyst in NaBH4 hydrolysis reaction to hydrogen generation

This paper reports the experimental results on using TiO₂ based Cu(II)-Schiff Base complex catalyst for hydrolysis of NaBH₄. In the presence of Cu-Schiff Base complex which we reported in advance [1] and with titanium dioxide supports a novel catalyst named TiO₂ supported 4-4′-Methylenbis (2,6-diethyl)aniline-3,5-di-tert-buthylsalisylaldimine-Cu complex is prepared, successfully. The synthesized catalyst was characterized by means of X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller Surface Area Analysis (BET) and Fourier Transform Infrared Spectroscopy (FT-IR). The as prepared catalyst was employed to generate hydrogen through hydrolysis reaction of NaBH₄. Effects of different parameters (e.g. amount of Cu-Schiff Base complex in all catalyst, percentage of NaBH₄, percentage of NaOH, amount of TiO₂ supported Cu-Schiff Base complex catalyst and different temperatures) are also investigated. A high apparent activation energy (Ea), 25,196 kJ.mol^-1 is calculated for hydrolysis of NaBH₄ at 20–50 °C. Hydrogen generation rate was 14,020 mL H₂/g_cat.min and 22,071 mL H₂/g_cat.min in order of 30 °C and 50 °C.     

Poly (acrylic acid)/polysaccharides IPN derived metal free catalyst for rapid hydrogen generation via NaBH4 methanolysis

Polymeric catalysts have displayed great performance for catalytic hydrogen generation. However, the reported metal free polymeric catalysts for NaBH₄ methanolysis are mainly limited to coating strategy where the catalytic activity fade after few cycles. Herein, we report an interpenetrating polymer network (IPN) strategy for rapid and highly recyclable NaBH₄ catalytic methanolysis to produce hydrogen (H₂) gas. In this study, we prepared poly(acrylic acid)/polysaccharide IPN via Pickering tempted polymerization. The hydrogen generation performance was studied employing different parameters where maximum HGR of 8182 mL H₂ min^?1 g^?1 of CAP. The activation energy Ea, enthalpy and entropy were calculated to be 62.99 kJ mol^?1, 32.25 kJ mol and ?130.92 J mol K^?1, respectively. Above all, CAP kept cyclic performance to 100% even at the 7th cycle. We confirmed the reproducibility of approach with other natural polysaccharides. This was due to strong chain entanglement of IPN synthesis which forces the active sites to stay in place during cyclic catalysis reaction. Thus, the IPN strategy ensures longer catalyst life for catalytic methanolysis of NaBH₄ for H₂ generation.     

Metal nanoparticles supported on polyacrylamide water beads as catalyst for efficient generation of H2 from NaBH4 methanolysis

Water beads made from polyacrylamide polymer p-(AAm) were decorated with high efficient metal nanoparticles by inexpensive, fast, simple, and environmental friendly method. These water beads balls were kept in the metal salt solutions for 4 h; to adsorb the metals ions from these aqueous solutions. The metal ions decorated on the p-(AAm) water beads were converted to metal nanoparticles by its reduction with aqueous solution of NaBH₄. The prepared materials p-(AAm) loaded with MNPs (M@p-(AAm)) were characterized by ATR-FTIR, XRD, XPS, FESEM, and EDS which show the successful preparation of MNPs over the surface and within p-(AAm). Afterwards the M@p-(AAm) were investigated as a catalyst for the generation of hydrogen from the methanolysis of NaBH₄. The Ag@p-(AAm) show good catalytic activity for NaBH₄ methanolysis reaction as compared to the other loaded MNPs. In addition, different parameters which effecting H₂ generation were also investigated such as; MNPs types, catalyst amount and temperature of the reaction. Low activation energy (Ea) of 21.37 ± 0.67 kJ mol⁻¹, was calculated for NaBH₄ methanolysis reaction at temperature ranging from 5.0 °C to 35 °C. Moreover, the catalyst reusability was also studied and found no decrease in percent conversion, however percent efficiency was decreases about 37% after completion of four cycles.     

Catalytic methanolysis and hydrolysis of hydrazine-borane with monodisperse Ru NPs@nano-CeO2 catalyst for hydrogen generation at room temperature

Herein, we report metal catalyzed methanolysis and hydrolysis of hydrazine-borane as a fast hydrogen generation system under mild conditions. To the best of our knowledge, this is the first report that a monodisperse Ru NPs@nano-CeO₂ catalyst can achieve a complete conversion of N₂H₄BH₃ to H₂ with the assistance of both methanolysis and hydrolysis reactions. In order to achieve hydrolysis and methanolysis effectively, monodisperse Ru NPs@nano-CeO₂ catalyst have been prepared by modifying the chemical reduction method which is a very simple and efficient method in room conditions. The synthesized Ru NPs@nano-CeO2 catalyst showed excellent catalytic activity, stability, and selectivity in the production of hydrogen by both hydrolysis and methanolysis of the hydrazine-borane. The results reported here also includes (i) identification of the prepared catalyst by using analytical techniques such as XRD, XPS, TEM, HR-TEM, (ii) determination of stoichiometry for methanolysis and hydrolysis reactions, (iii) determination of rate constants and laws for methanolysis and hydrolysis reactions, (iv) determination of kinetic parameters such as enthalpy, entropy and activation energy for methanolysis and hydrolysis reactions.     

Electrochemical fabrication of novel platinum-poly(5-nitroindole) composite catalyst and its application for methanol oxidation in alkaline medium

A novel composite catalyst, Pt nanoparticles supported on poly(5-nitroindole) (Pt/PNI), has been successfully prepared by the electrochemical method and used for the electrooxidation of methanol in alkaline media. As-prepared Pt/PNI was characterized by SEM, EDX and electrochemical methods. The results of the catalytic activity for methanol oxidation showed that Pt/PNI had higher catalytic activity and stronger poisoning-tolerance than Pt/Pt, Pt/GC and the common Pt electrode. The effects of different parameters related to the methanol oxidation reaction kinetics, such as Pt loading, mass of PNI film, concentration of methanol and KOH, potential scan rate, have also been investigated. The present study showed a promising choice of Pt/PNI as composite catalyst for methanol electrooxidation in alkaline medium.     

Zeolite confined copper(0) nanoclusters as cost-effective and reusable catalyst in hydrogen generation from the hydrolysis of ammonia-borane

Herein we report the development of a cost-effective nanocluster catalyst for the hydrolytic dehydrogenation of ammonia-borane which is considered to be one among the new hydrogen storage materials. Zeolite confined copper(0) nanoclusters were prepared by the ion-exchange of Cu²⁺ ions with the extra framework Na⁺ ions in zeolite-Y followed by reduction of the Cu²⁺ ions within the cavities of zeolite with sodium borohydride in aqueous solution and characterized by HR-TEM, XRD, XPS, SEM, EDX, ICP-OES, Raman spectroscopy and N₂ adsorption–desorption technique. Zeolite confined copper(0) nanoclusters are found to be active catalysts in the hydrolysis of ammonia-borane even at low temperatures (≤15 °C) and stable enough for being isolated as solid materials. They provide 1300 turnovers in hydrogen generation from the hydrolysis of ammonia–borane at room temperature. The average value of turnover frequency is 46.5 h⁻¹ for the same reaction. More importantly, zeolite confined copper(0) nanoclusters were found to be isolable, bottleable and reusable catalysts in the hydrolytic dehydrogenation of ammonia-borane; even at fifth run the complete release of hydrogen from the hydrolysis of ammonia-borane at room temperature is achieved. The work reported here also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy and the effect of catalyst concentration on the rate for the catalytic hydrolysis of ammonia–borane.     

Effect of Al2O3-supported Cu-Schiff base complex as a catalyst for hydrogen generation in NaBH4 hydrolysis

Cu-Schiff base complex which we previously synthesized (Kilinc et al., 2012) is supported on Al₂O₃. The prepared catalyst is characterized by using SEM, XRD, BET, and FT-IR methods. And Al₂O₃-supported complex is used as a catalyst in NaBH₄ hydrolysis reaction for hydrogen generation. NaBH₄ hydrolysis reactions are investigated depending on the concentration of NaBH₄ and NaOH, temperature, percentage of Cu complex, and amount of catalyst. Maximum reaction rates are 44,453.33 and 57,410.00 mL H₂/g.cat.min at 30°C and 50°C, respectively. The activation energy of NaBH₄ hydrolysis reaction is found as 225,775 kJ^.mol^?1. All the experimental results and literature comparisons show that Al₂O₃-supported Cu-Schiff base complex is a very effective catalyst in NaBH₄ hydrolysis for H₂ generation.     

From plastic-waste to H2: A first approach to the electrochemical reforming of dissolved Poly(methyl methacrylate) particles

The development of sustainable processes for the recycling of plastic is a major environmental issue to reduce the pollution by this kind of waste. The electro-oxidation of plastic wastes in electrolysers powered by renewable energies is a promising option to produce hydrogen at low temperature while diminishing the energy demand compared to Oxygen Evolution Reaction (OER). Poly (methyl-methacrylate) (PMMA) particles, a widely used polymer, were dissolved (0.1–2% wt.) in an isopropanol(IPA)/H₂O binary solvent and electro-oxidized on Pt/C-based electrodes in a liquid batch electrochemical cell at 70 °C in acidic media. Despite the dissolution strategy, polymer macromolecules partially block the accessibility of the active sites of a commercial electrode and strongly degrades its electrochemical performances mainly linked to IPA electro-oxidation. The preparation of a more porous electrode supported on carbon paper was found to strongly hinder this deactivation. Furthermore, the electrooxidation of PMMA or PMMA-derived molecules can be performed during cyclic voltammetries up to 1.4 V and chrono-amperometries at 1.4 V.     

Monodispersed p(2-VP) and p(2-VP-co-4-VP) particle preparation and their use as template for metal nanoparticle and as catalyst for H2 production from NaBH4 and NH3BH3 hydrolysis

The monodispersed poly(2-vinyl pyridine) (p(2-VP)) and poly(2-vinyl pyridine-co-4-vinyl pyridine) (p(2-VP-co-4-VP)) particles of different compositions were synthesized by a surfactant-free emulsion polymerization system using divinyl benzene (DVB) as cross-linker. The diameter of p(2-VP) and p(2-VP-co-4-VP) particles were measured between 370 and 530 nm. Co, Ni and Cu metal nanoparticles were prepared inside these microgels after quaternization with HCl and loading of metal salts, such as CoCl₂, NiCl₂, and CuCl₂, in ethyl alcohol followed by reduction with NaBH₄. The prepared metal nanoparticles within these particles were used as catalyst for H₂ production via hydrolysis of NaBH₄ and NH₃BH₃. Various parameters of the polymeric microgels such as template, metal types, reuse, the amount of NaOH, and temperature were investigated. From hydrolysis reactions the activation energy (E_a), enthalpy (ΔH), and entropy (ΔS) were calculated for Co metal nanoparticles as catalyst for the NaBH₄ hydrolysis reaction in the temperature range of 0–50 °C. The activation parameters of NaBH₄ hydrolysis catalyzed by Co nanoparticle composite systems were calculated as 46.44 ± 1.1 kJ mol⁻¹ for E_a, 36.39 ± 6.5 kJ mol⁻¹ for ΔH and −170.56 ± 20.1 kJ mol⁻¹ K⁻¹ for ΔS.     

Close-packed SiO2/poly(methyl methacrylate) binary nanoparticles-coated polyethylene separators for lithium-ion batteries

In an endeavour to improve not only the thermal shrinkage but also the electrochemical performance of separators in lithium-ion batteries, a novel composite separator is developed, i.e., a close-packed SiO₂/poly(methyl methacrylate) (PMMA) binary nanoparticles-coated polyethylene (PE) separator. The introduction of SiO₂ nanoparticles to the coating layer effectively suppresses thermal shrinkage of the composite separator. In contrast to a SiO₂/PMMA coating layer having a film-shaped PMMA binder, the SiO₂/PMMA binary nanoparticle coating layer employs PMMA particles as a binder. As a consequence, a highly porous structure, i.e., well-connected interstitial voids, is formed between the binary SiO₂ and PMMA nanoparticles. The unique porous morphology allows favourable liquid electrolyte wettability and facile ionic conduction, which play a crucial role in improving cell performance such as the discharge capacity and the C-rate capability of the composite separator.     

Tungsten(VI) oxide supported rhodium(0) nanoparticles; highly efficient catalyst for H2 production from dimethylamine borane

It reports the preparation and characterization of tungsten(VI) oxide supported rhodium(0) nanoparticles (Rh⁰/WO₃ NPs) being used as catalysts in releasing H₂ from dimethylamine borane (DMAB). The reducible nature of WO₃ plays a significant role in the catalytic efficiency of rhodium(0) nanoparticles in the dehydrogenation of DMAB. The Rh⁰/WO₃ NPs were in-situ generated from the reduction of Rh²⁺ ions on the surface of WO₃ during the catalytic dehydrogenation of dimethylamine borane in toluene and isolated from the reaction solution after the dehydrogenation to be characterized by using SEM, TEM, XPS, ATR-IR and XRD. The results reveal the formation of Rh⁰ NPs with a mean particle size of 1.92 ± 0.34 nm dispersed on the surface of tungsten(VI) oxide. Rh⁰/WO₃ NPs are found to be very active catalyst releasing 1.0 equiv. H₂ per mole of dimethylamine borane under ambient conditions. Among the various WO₃ supported Rh⁰ NPs with different metal loadings, the sample with 0.1% wt. Rh provide the record catalytic activity (TOF = 2816 h^?1) which is one of the highest value ever reported for rhodium-based catalysts in H₂ generation from DMAB at 60.0 ± 0.5 °C. Rh⁰/WO₃ NPs were also reusable catalyst in dehydrogenation of DMAB retaining 55% of their initial catalytic activity in the 3rd run of the dehydrogenation reaction. Control experiments were performed at various catalyst concentrations and temperatures to investigate the kinetics of dehydrogenation and to calculate the activation parameters for the reaction.     

Poly(vinylidene fluoride) based anion conductive ionomer as a catalyst binder for application in anion exchange membrane fuel cell

An anion conductive polymeric ionomer incorporated into the electrodes of an anion exchange membrane fuel cell (AEMFC) can help to enhance anion transport in the catalyst layer of electrode, and thus improve the catalyst efficiency and performance of AEMFC. In this work, we report the synthesis and properties of a new type of anion conductive ionomer, which is synthesized by grafting of poly(vinylidene fluoride), or PVDF with poly(vinylbenzyltrimethylammonium chloride) via atom transfer radical polymerization. The ionomer obtained shows improved hydrophilicity relative to pristine PVDF, and exhibits an ion exchange capacity of 1.59 mmol g⁻¹. When used in a direct hydrazine hydrate fuel cell (DHFC) as a catalyst binder, the synthesized ionomer imparts the DHFC a significantly improved power density, which is 5-10 fold as much as that of the cells without using such ionomer. The method developed here for anion exchange ionomer synthesis is facile, green and does not involve the use of carcinogenic chemicals such as chloromethylmethylether and trimethylamine, which are often used for conventional anion exchange membrane or ionomer synthesis.     

Water soluble laurate-stabilized ruthenium(0) nanoclusters catalyst for hydrogen generation from the hydrolysis of ammonia-borane: High activity and long lifetime

The simplest amine-borane, considered as solid hydrogen storage material, ammonia-borane (H₃NBH₃) can release hydrogen gas upon catalytic hydrolysis under mild conditions. Herein, we report the preparation of a novel catalyst, water dispersible laurate-stabilized ruthenium(0) nanoclusters from the dimethylamine-borane reduction of ruthenium(III) chloride in sodium laurate solution at room temperature. The ruthenium nanoclusters in average size of 2.6 ± 1.2 nm were isolated from the solution and well characterized by using TEM, XPS, FTIR, and UV–visible electronic absorption spectroscopy. The water dispersible laurate-stabilized ruthenium(0) nanoclusters were found to be highly active and long-live catalyst with a TOF of 75 mol H₂/mol Ru·min and TTO value of 5900 mol H₂/mol Ru in the hydrolysis of ammonia-borane at 25.0 ± 0.1 °C.     

Metal nanoparticle-embedded super porous poly(3-sulfopropyl methacrylate) cryogel for H2 production from chemical hydride hydrolysis

Poly(3-sulfopropyl methacrylate) (p(SPM)) cryogel was prepared under cryogenic conditions (T = −18 °C) and used as template for in situ metal nanoparticle preparation of Co, Ni and Cu. These metal nanoparticle-containing super macroporous cryogel composites were tested for H₂ production from hydrolysis of sodium borohydride (NaBH₄) and ammonia borane (AB). It was found that amongst p(SPM)-M (M: Co, Ni, and Cu) composite catalyst systems, the catalytic performances of Co- and Ni-containing p(SPM) cryogel composite catalyst systems were the same, however in hydrolysis of NH₃BH₃, the order of performance of the catalysts was Co > Ni > Cu. Interestingly, p(SPM)-Co cryogel composite demonstrated better catalytic performances in salt environments e.g., faster H₂ production rate in sea and tap water compared to DI water, and almost no effect of ionic strength of the solution medium was observed, but the salt types were found to affect the H₂ generation rate. Other parameters that affect H₂ production rate such as metal type, temperature, water source, salt concentration, amount of metal nanocatalyst and reusability were investigated. It was found that the hydrogen generation rate (HGR) was increased to 2836 ± 90 from 1000 ± 53 (ml H₂)(g of Co min)⁻¹ by multiple loading and reduction cycles of Co catalyst. Also, it was found that TOF values are highly temperature dependent, and increased to 15.1 ± 0.8 from 2.4 ± 0.1 (mol H₂)(mol catalyst min)⁻¹ by increasing the temperature from 30 to 70 °C. The activation energy, activation enthalpy and activation entropy were determined as 40.8 kJ (mol)⁻¹, 37.23 kJ (mol K)⁻¹, and −170.87 J (mol K)⁻¹, respectively, for the hydrolysis reaction of NaBH₄ with p(SPM)-Co catalyst system, and 25.03 kJ (mol)⁻¹, 22.41 kJ (mol K)⁻¹, and −182.8 J (mol K)⁻¹, respectively, for AB hydrolysis catalyzed by p(SPM)-Co composite system.     

Silica embedded cobalt(0) nanoclusters: Efficient, stable and cost effective catalyst for hydrogen generation from the hydrolysis of ammonia borane

Cobalt(0) nanoclusters embedded in silica (Co@SiO₂) were prepared by a facile two-step procedure. In the first step, the hydrogenphosphate anion (HPO₄²⁻) stabilized cobalt(0) nanoclusters were in situ generated from the reduction of cobalt(II) chloride during the hydrolysis of sodium borohydride (NaBH₄) in the presence of stabilizer. Next, HPO₄²⁻ anion-stabilized cobalt(0) nanoclusters were embedded in silica formed by in situ hydrolysis and condensation of tetraethylorthosilicate added as ethanol solution. Co@SiO₂ can be separated from the solution by vacuum filtration and characterized by UV-Vis electronic absorption spectroscopy, TEM, SEM-EDX, ATR-IR and ICP-OES techniques. Co@SiO₂ are found to be highly active and stable catalysts in the hydrolysis of ammonia borane (AB) even at low cobalt concentration and room temperature. They provide an initial turnover frequency of 13.3 min⁻¹ and 24,400 total turnovers over 52 h in the hydrolysis of AB at 25.0 ± 0.5 °C. Moreover, Co@SiO₂ retain 72% and 74% of the initial activity after ten runs recyclability and five cycles reusability test in the hydrolysis of AB, respectively. The kinetics of hydrogen generation from the hydrolysis of AB catalyzed by Co@SiO₂ was studied depending on the catalyst concentration, substrate concentration, and temperature. The activation parameters of this catalytic reaction were also determined from the evaluation of the kinetic data.     

Phosphorylated chitosan/poly(vinyl alcohol) based proton exchange membranes modified with propylammonium nitrate ionic liquid and silica filler for fuel cell applications

In our previous work, phosphorylated chitosan was modified through polymer blending with poly(vinyl alcohol) (PVA) polymer to produce N-methylene phosphonic chitosan/poly(vinyl alcohol) (NMPC/PVA) composite membranes. The aim of this work is to further investigate the effects of a propylammonium nitrate (PAN) ionic liquid and/or silicon dioxide (SiO₂) filler on the morphology and physical properties of NMPC/PVA composite membranes. The temperature-dependent ionic conductivity of the composite membranes with various ionic liquid and filler compositions was studied by varying the loading of PAN ionic liquid and SiO₂-PAN filler in the range of 5–20 wt%. As the loading of PAN ionic liquid increased in the NMPC/PVA membrane matrix, the ionic conductivity value also increased with the highest value of 0.53 × 10^?3 S cm^?1 at 25 °C and increased to 1.54 × 10^?3 S cm^?1 at 100 °C with 20 wt% PAN. The NMPC/PVA-PAN (20 wt%) composite membrane also exhibited the highest water uptake and ion exchange capacity, with values of 60.5% and 0.60 mequiv g^?1, respectively. In addition, in the single-cell performance test, the NMPC/PVA-PAN (20 wt%) composite membrane displayed a maximum power density, which was increased by approximately 14% compared to the NMPC/PVA composite membrane with 5 wt% SiO₂-PAN. This work demonstrated that modified NMPC/PVA composite membranes with ionic liquid PAN and/or SiO₂ filler showed enhanced performance compared with unmodified NMPC/PVA composite membranes for proton exchange membrane fuel cells.     

Composite membranes based on sulfonated poly(aryl ether ketone)s containing the hexafluoroisopropylidene diphenyl moiety and poly(amic acid) for proton exchange membrane fuel cell application

Composite membranes based on sulfonated poly(aryl ether ketone)s containing the hexafluoroisopropylidene diphenyl moiety and poly(amic acid) with oligoaniline in the main chain have been prepared and immersed in H₃PO₄ to obtain acid-doped composite films. As expected, the water uptake values and methanol permeability of the composite membranes decrease with the increase of the weight fraction of PAA in the membrane matrix. Notably, the SPEEK-6F/PAA-15 shows a water uptake of 13.2% and a methanol permeability of 0.9 × 10⁻⁷ cm² s⁻¹, which are much lower than those of the Nafion (28.6% and 15.5 × 10⁻⁷ cm² s⁻¹, respectively). Although the proton conductivities decrease after the addition of PAA, higher selectivity values are obtained with the composite membranes. Therefore, the SPEEK-6F/PAA blend membranes, with the improved proton conductivity, methanol resistance and good thermal stability, can be used as a good alternative for proton conductive membranes with potential application in proton exchange membrane fuel cells (PEMFCs).