Biocomposite proton‐exchange membrane electrolytes for direct methanol fuel cells

Poly(vinyl alcohol) (PVA)‐amino acid (AA) biocomposite membranes are prepared by blending PVA with AAs such as glycine, lysine (LY), and phenyl alanine followed by in situ crosslinking with citric acid (CA) and explored as a new class of biocomposite membrane electrolytes for direct methanol fuel cells (DMFCs). CA crosslinks with PVA through esterification offers adequate chemical, thermal, and morphological stability thereby produces methanol‐obstructing close‐packed polymeric network. These biocomposite membranes are characterized in terms of mechanical, thermal, sorption, and proton‐conducting properties. Hydrophilic nature of AA zwitterions significantly facilitates proton conduction and CA crosslinking mitigates methanol crossover through establishing appropriate balance between hydrophilic/hydrophobic domains. The rational design of membrane microstructure with proper arrangement of hydrophobic/hydrophilic domains is a key to enhance electrochemical selectivity of PVA‐AA/CA biocomposite membranes. Biocomposite membrane comprising LY exhibits nearly threefold higher electrochemical selectivity in relation to PVA/CA blend membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43514.     

Electrospinning preparation of a graphene oxide nanohybrid proton‐exchange membrane for fuel cells

Proton‐exchange membrane (PEM) is a core component of fuel cells that provides a channel for proton migration and transport. Prevailing PEMs fabricated using well‐established casting techniques have several limitations such as low proton conductivity, high fuel permeability, and poor stability. To overcome these shortcomings, this article introduces a graphene oxide (GO)‐based nanohybrid Nafion nanofiber membrane prepared using a facile electrospinning technique. On the one hand, electrospinning nanofibers provide efficient transport paths for protons, which tremendously enhance the proton conductivity. On the other hand, GO doping in PEM improves the self‐humidification, stabilities (mechanical, thermal, and chemical), and proton conductivity and reduces the fuel permeability. In this research, nanofiber membranes were obtained from Nafion solutions containing 0, 0.1, and 0.2 wt % GO via electrospinning. The morphology, structure, mechanical properties, proton conductivity, water uptake, and swelling properties of the membranes were studied. The results demonstrated that the comprehensive performance of PEM was significantly improved. The new findings may promote the wide application of PEM fuel cells. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46443.     

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

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

Synthesis and properties of fluorine‐ and siloxane‐containing polybenzimidazoles for high temperature proton exchange membrane fuel cells

In this study, new fluorine–siloxane‐containing polybenzimidazole (PBI) copolymers were synthesized by copolymerization of 3,3′‐diaminobenzidine, 2,2‐bis(4‐carboxyphenyl)‐hexafluoropropane (HFA), and 1,3 bis(carboxypropyl)tetramethyldisiloxane (BTMDS) with different molar ratios. PBI copolymer membranes were prepared by solution‐casting and then doped with phosphoric acid. The structures of PBI copolymers were characterized by FTIR and X‐ray diffraction. The solubility of the PBI copolymers was significantly increased by the introduction of the bulky HFA group and the flexible BTMDS group into the polymer backbone. The PBI copolymers still maintained good thermal stability and mechanical properties. Because of the introduction of the flexible and hydrophobic siloxane group in the polymer backbone, the methanol permeability was reduced and the proton conductivity under anhydrous condition at high temperatures was increased compared to the PBI without the siloxane group. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4107–4112, 2013     

Sulfonated poly(ether sulfone)‐based catalyst binder for a proton‐exchange membrane fuel cell

Sulfonated poly(ether sulfone) copolymer (PES 60) and its partially fluorinated analogue (F‐PES 60) were synthesized via the nucleophilic aromatic polycondensation of commercially available monomers to make a polymer electrolyte membrane and a binding material in the electrodes of a membrane–electrode assembly (MEA). PES 60 and F‐PES 60 showed proton conductivities of 0.091 and 0.094 S/cm, respectively, in water at room temperature. The copolymer was dissolved in the mixture of alcohol and water to get a 1 wt % binder solution. A catalyst slurry was prepared with the copolymer solution and sprayed on the copolymer (PES 60 or F‐PES 60) membrane to obtain a MEA. Both PES 60 and F‐PES 60 based MEAs were fabricated with different amounts of their binder in the electrodes to examine the effect of the copolymer binder in the catalyst layer on the fuel cell performance. The MEA with 2 wt % copolymer binder in the electrodes showed the best fuel cell performance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of a proton‐exchange membrane by the radiation grafting of styrene onto polytetrafluoroethylene films

Radiation‐induced simultaneous grafting of styrene onto polytetrafluoroethylene (PTFE) films and the subsequent sulfonation in the chlorosulfonic acid/dichloroethane were investigated. The effects of the main radiation grafting conditions, such as the type of solvents, irradiation dose, dose rate, the styrene concentrations, etc., on the degree of grafting (DOG) were studied. To elucidate the influence of both the grafting and sulfonation conditions on the properties of the PTFE‐g‐polystyrene‐sulfonic acid (PSSA) membranes, the sulfonation conditions, including the sulfonation temperature and the concentration of the ClSO₃H with respect to the DOG, were systematically evaluated. The grafted and sulfonated membranes were characterized by FTIR–ATR spectra, ion‐exchange capacity (IEC), water uptake, thickness measurement, etc. The as‐prepared PTFE‐g‐PSSA membranes in this work showed a good combination of a high IEC (0.85–2.75 meq g^?1), acceptable water uptake (8.86–56.9 wt %), low thickness, and volume expansion and/or contraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1415–1428, 2006     

Poly(vinyl alcohol) modified by KE reactive dyes as a novel proton‐exchange membrane for potential fuel‐cell applications

A new type of proton‐exchange membrane based on poly(vinyl alcohol) (PVA) modified KE reactive dyes (KE‐4BD) was prepared and evaluated as H⁺‐conducting polymer electrolytes. The effects of the content of KE‐4BD on the membrane H⁺ conductivity and water uptake were studied with an alternating‐current impedance technique and the method of weighing, respectively. Fourier transform infrared and scanning electron microscopy were used for the chemical and structural characterization of these membranes. With all of these properties, the optimal mass ratio between PVA and KE‐4BD was 1:0.5, and the resulting membrane exhibited a high proton conductivity (0.109 S/cm) at room temperature; this afforded a power density of 83.9 mW/cm² at 210.4 mA/cm² and an open‐circuit voltage of 810.8 mV. The PVA/KE‐4BD membranes showed a high oxidative stability in Fenton's reagent (3% H₂O₂ v/v, 2 ppm FeSO₄). Thermal analysis also showed that the membranes exhibited a significant improvement in thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43019.     

Synthesis and characterization of a novel high‐oil‐absorbing resin

A high‐oil‐absorbing resin, which was a low crosslinking resin, was synthesized by conventional suspension copolymerization in this study. The effects of the monomer ratio, crosslinker, initiator, ratio of water to oil, and defined optimum reaction conditions were studied. The highest oil absorptivity of the resin was about 11.5 g/g in diesel and the oil‐absorption saturation time was 3 days when the best process conditions were as follows: ratio of styrene to ethylene–propylene–diene terpolymer = 40/60 w/w, amount of crosslinker divinylbenzene = 1.0 wt %, amount of benzoyl peroxide = 1.0 wt %; proportion of gelatin to calcium phosphate = 0.2 g/0.1 g, stirring speed = 500 r/min, and proportion of water to oil = 15 : 1. By using such methods as infrared spectroscopy, thermogravimetric analysis, and other methods, we studied the oil‐absorbing resin structure, oil‐absorption rate, oil‐absorption saturation time, and oil‐absorption rate twice. The oil‐absorbing resins were used repeatedly through the extraction of ethanol. The experiment results show little effect on the oil‐absorption properties. The oil‐absorption rate constant was evaluated for diesel, and the oil‐absorbing process obeyed the first‐order kinetics equation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and properties of sulfonated poly(arylene ether nitrile) copolymers containing carboxyl groups for proton‐exchange membrane materials

A series of sulfonated poly(arylene ether nitrile) copolymers containing carboxyl groups were synthesized via a nucleophilic aromatic substitution reaction from phenolphthalein, hydroquinone sulfonic acid potassium salt, and 2,6‐difluorobenzonitrile in N‐methyl pyrrolidone (NMP) with K₂CO₃ as a catalyst. The synthesized copolymers had good solubility in common polar organic solvents and could be easily processed into membranes from solutions of dimethyl sulfoxide, NMP, N,N′‐dimethyl acetylamide, and dimethylformamide. Typical membranes in acid form were gained, and the chemical structures of these membranes were characterized by Fourier transform infrared analysis. The thermal properties, fluorescence properties, water uptake, ion‐exchange capacity, and proton conductivities of these copolymers were also investigated. The results indicate that they had high glass‐transition temperatures in the range 151–187°C and good thermal stability, with the 10 wt% loss temperatures ranging from 330 to 351°C under nitrogen. The copolymers showed characteristic unimodal ultraviolet–visible (UV–vis) absorption and fluorescence emission, and the UV–vis absorption, fluorescence excitation, and emission peaks of the copolymers were obvious. Moreover, the copolymer membranes showed good water uptake and proton conductivities at room temperature and 55% relative humidity because of the introduction of both sulfonic acid groups and carboxyl groups into the copolymers, whose contents were in ranges 18.45–67.86 and 3.4 × 10^?4 to 3.0 × 10^?3 s/cm, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40213.     

Physicochemical characterization of low sulfonated polyether ether ketone/Smectite clay composite for proton exchange membrane fuel cells

Polyether ether ketone (PEEK) with a low sulfonation degree was blended using different proportions of sodium rich Smectite clay (3 and 6 wt%) to use as an electrolyte membrane for fuel cell application. The structural functionalities, surface morphologies, and the thermal stability of the resultant composite membranes were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, atom force microscopy, and thermo-gravimetric analysis. FT-IR showed that no chemical reactions take place between the sulfonated polyether ether ketone (SPEEK) and the clay with different ratios. XRD diffractograms illustrated a lower degree of crystallinity of the blended SPEEK than pristine SPEEK. The elaborated composite membranes proved to have a higher thermal stability than SPEEK. Furthermore, the SPEEK/clay composite membranes with 3 and 6 wt% in clay loading had higher water uptake and lower methanol uptake than those in pristine SPEEK It was also shown that, the incorporation of sodium ions rich Smectite clay layers between the clusters in SPEEK improved the conductivity to 2 × 10⁻² S/cm at 140°C (for 6 wt% in clay) without compromising the dimensional stability of the composite membranes. These results propose the composite membranes as a potential candidate for methanol fuel cells at temperatures above 120°C making SPEEK composite membrane competitive to that of Nafion membrane.     

Studies on a novel anion‐exchange membrane based on chitosan and ionized organic compounds with multiwalled carbon nanotubes for alkaline fuel cells

In this work, a novel hydroxyl‐anion‐conducting membrane composed of chitosan (CTS), an ionized organic compound ([QAIM]OH), and hydroxylated multiwalled carbon nanotubes (MWCNTs‐OH) has been fabricated through a blending‐casting method assisted by a glutaraldehyde (GA) crosslinking process that can improve the mechanical properties of the membrane effectively. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy revealed that [QAIM]OH and MWCNTs‐OH were successfully introduced into the CTS matrix. A chemical crosslinking reaction between CTS and GA could be confirmed by FTIR, X‐ray photoelectron spectroscopy, and contact angle tests. By tuning the mass fraction of [QAIM]OH and MWCNTs‐OH in the membrane, the maximum OH^? conductivity (5.66 × 10^?3 S cm^?1 at room temperature) could be achieved for the composition CTS:[QAIM]OH (1:0.75 in mass) blend doped with 3% MWCNTs‐OH. At a current density of 59.9 mA cm^?2, a membrane electrode assembly fabricated with the CTS/[QAIM]OH/ MWCNTs‐OH membrane (1:0.5/3%) achieved a power density of 31.6 mW cm^?2 in a H₂/O₂ system at room temperature. Under the condition of intermediate temperature (100–140 °C) without water, the conductivities of the membranes increased with increasing temperature and the amount of [QAIM]OH, which acted as an ionic liquid in the membrane, indicating that the ionic transport behaviors could still be occurring. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46323.     

Recent developments in fuel‐processing and proton‐exchange membranes for fuel cells

In recent years, great progress has been made in the development of proton‐exchange membrane fuel cells (PEMFCs) for both mobile and stationary applications. This review covers two types of new membranes: (1) carbon dioxide‐selective membranes for hydrogen purification and (2) proton‐exchange membranes; both of these are crucial to the widespread application of PEMFCs. On hydrogen purification for fuel cells, the new facilitated transport membranes synthesized from incorporating amino groups in polymer networks have shown high CO₂ permeability and selectivity versus H₂. The membranes can be used in fuel processing to produce high‐purity hydrogen (with less than 10 ppm CO and 10 ppb H₂S) for fuel cells. On proton‐exchange membranes, the new sulfonated polybenzimidazole copolymer‐based membranes can outperform Nafion^® under various conditions, particularly at high temperatures and low relative humidities. Copyright © 2010 Society of Chemical Industry     

A synthesis study of phosphonated PSEBS for high temperature proton exchange membrane fuel cells

A series of novel phosphonated proton exchange membranes has been prepared using poly(styrene‐ethylene/butylene‐styrene) block copolymer (PSEBS) as base material. Phosphonic acid functionalization of the polymer was performed by a simple two‐step process, via chloromethylation of PSEBS followed by phosphonation utilizing the Michaels–Arbuzov reaction. The successful phosphonation of the polymers were characterized by NMR and Fourier transform infrared. The phosphonated ester form of the membranes were obtained by solvent evaporation method and hydrolyzed to get a proton conducting membrane. The membrane properties such as ion exchange capacity, water uptake and proton conductivity at various temperatures were examined for their suitability to be utilized as a high temperature polymer electrolyte. Additionally, the morphology, thermal, and mechanical properties of the synthesized membranes were investigated, using scanning electron microscope, thermogravimetric analysis, and tensile test, respectively. The effective (anhydrous) proton conductivity was studied with respect to various degrees of functionalization. From the studies, the membranes were found to have a comparatively good conductivity and one of the membranes reached the maximum value of 5.81 mS/cm² at 140 °C as measured by impedance analyzer. It was found that the synthesized membranes were mechanically durable, chemically, and thermally stable. Hence, the synthesized phosphonated membranes could be a promising candidate for high temperature polymer electrolyte fuel cell applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45954.     

Synthesis and characterization of bio‐based PA/EP interpenetrating network polymer as coating material for controlled release fertilizers

A novel controlled release fertilizer was developed using interpenetrating polymer network (IPN) as the coating material. The IPN was successfully sprayed on the surface of the urea particles to form IPN‐coated fertilizers (IPNCU) for controlled nitrogen release. The IPN was synthesized by bio‐based polyamide (PA) from d ‐glucaric acid and epoxy (EP) through network interpenetrating. The chemical structure and microscopic morphology characteristics of IPN were examined by Fourier transform infrared spectroscopy, ¹H‐nuclear magnetic resonance, and scanning electron microscopy. The property of IPN with the different PA/EP mass ratios were investigated and compared with that of EP‐coated fertilizers (EPCU). The nutrient release behaviors of IPNCU in water and soil were detected. The results showed that the IPNCU with 5% PA content increased the nitrogen release longevity by 41 days, raised the water contact angle of surface by 23.9°, and then significantly slowed the nitrogen release rate of the IPNCU. The nutrient release mechanism of IPNCU was discussed in detail. This work indicated that the environment‐friendly IPN with superior controlled release properties could be especially useful in horticultural and agricultural applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46052.     

Synthesis and characterization of novel polyureas based on benzimidazoline‐2‐one and benzimidazoline‐2‐thione hard segments

Six novel polyureas were prepared from benzimidazolin‐2‐one and benzimidazolin‐2‐thione, which acted as hard segments, with two aromatic diisocyanates (4,4′‐diphenylmethane diisocyanate and toluene 2,4‐diisocyanate) and one aliphatic diisocyanate (hexamethylene diisocyanate). The polymers that formed were fully characterized with Fourier transform infrared spectroscopy, ¹³C‐NMR cross‐polarization/magic‐angle spinning, differential scanning calorimetry, and thermogravimetry. X‐ray diffraction revealed that the polymers contained crystalline and amorphous regions that varied with the nature of the backbone structures. All the polyureas were insoluble in common organic solvents, and this made it difficult to investigate their solution properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 576–583, 2006     

Preparation of an anion‐exchange membrane by the amination of chlorinated polypropylene and polyethyleneimine at a low temperature and its ion‐exchange property

An anion‐exchange membrane was prepared by the amination of chlorinated polypropylene and polyethyleneimine at a low temperature and was investigated with respect to not only its physical properties but also its electrochemical properties. The degrees of amination were 50.16, 53.76, 57.11, and 65.29% at 30, 40, 50, and 55°C, respectively. The base polymer membrane had no water uptake, whereas that of the aminated polymer membrane was 0.254, 0.296, 0.298, and 0.319 g of H₂O/g of dry membrane, respectively, with increasing amination. The prepared membranes possessed an ion‐exchange capacity in the range of 1.257–2.000 mequiv/g of dry membrane and a fixed ion concentration in the range of 4.492–6.261 mequiv/g of H₂O. The ionic conductivity of the aminated polymer membrane was highest when the water uptake was highest. Those of the prepared membrane were in the range of 0.89 × 10^?2 to 1.36 × 10^?2 S/cm. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Crosslinked anion exchange membrane with improved membrane stability and conductivity for alkaline fuel cells

As a core component of anion exchange membrane (AEM) fuel cells, it has practical significance to improve the performance of AEMs. However, it is difficult to obtain AEM with both good stability and high conductivity. In this study, a series of AEMs were prepared by chloromethylation, quaternization, and crosslinking reactions. The quaternization reaction was carried out first to ensure that there are abundant quaternary ammonium groups on AEM and enhance the conductivity of membrane. N,N,N′,N′-tetramethylethylenediamine was used as a crosslinker to improve membrane stability and mechanical property. A simple, mild, and cost-effective AEM synthetic route was developed. This strategy achieves a certain balance of electrochemical and physical properties. The effect of the crosslinking reactions on the property of membrane was evaluated. Crosslinked membranes have better dimensional stability (water uptake: 20.2% and swelling ratio: 2.1%), mechanical properties (55.84 MPa), and alkaline stability because crosslinked structures result in large steric hindrance. The mutually independent quaternization and crosslinking reaction do not affect the electrochemical performance of membranes; in the crosslinking reaction stage, crosslinker also reacted as quaternization agent and increased the number of reactive groups in AEM. Thus, the resulting crosslinked AEM exhibits higher ion exchange capacity and ionic conductivities (46.4 mS cm⁻¹). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48169.     

Preparation and characterization of proton‐exchange hybrid membranes

Two types of composite were prepared, based on a thermoplastic polymer, polyvinylidene fluoride (PVDF), and an elastomer, ethylene‐propylene‐diene terpolymer (EPDM), respectively. We obtained both series by addition of an inorganic proton‐conducting antimonic acid derivative (HSb) and polystyrene crosslinked with a small percentage of divinylbenzene (PS‐co‐DVB). From these composites, membranes were obtained and subjected to a heterogeneous‐phase sulfonation reaction with chlorosulfonic acid. All experimental materials were characterized from a morphological and electrical point of view, by means of techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), non‐isothermal crystallization and complex impedance analysis. Copyright © 2005 Society of Chemical Industry     

Preparation and characterization of cardanol‐based epoxy resin for coating at room temperature curing

Novel organic solvent‐free bio‐based epoxy resin for coating was prepared from cashew nut shell liquid which is one of renewable resources. The epoxy coating was fabricated by the reaction between amine compounds and epoxy cardanol prepolymer (ECP). The drying, physical, and thermal properties of the epoxy were investigated and compared with those of the commercial cashew coating. The ECP was synthesized by thermal polymerization under the various conditions. Based on the FT‐IR analysis, hydroxyl and carbonyl groups were generated, and viscosity increased with increasing heating temperature and time. On the other hand, the NMR analysis showed decrease in the degree of unsaturation in the side group of cardanol. Based on these results, the polymerization of the ECP could be autoxidized in the unsaturated group in the side chains. The drying time until harden dry of the ECP coating took about 2.5 h at room temperature, which is faster than that of the commercial cashew coating. This is because that the curing of ECP coating was based on the prepolymer (i.e., high molecular weight) and crosslink reaction between epoxy and amine groups. The ECP coating was rubbery state due to the flexible side chains of cardanol. Furthermore, the ECP coating improved chemical stability compared with the commercial cashew. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2468–2478, 2013