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.     

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     

碱性燃料电池用阴离子交换膜的研究进展

阴离子交换膜燃料电池（AEMFCs）因其具有环境友好、可使用非贵金属催化剂、电极反应速率快等特点而受到广泛关注。阴离子交换膜（AEMs）是AEMFCs的核心部件,其性质决定着燃料电池的性能、能量效率和使用寿命。从具有不同骨架结构的聚合物出发,介绍了聚苯醚、聚芳醚砜、聚烯烃和聚苯并咪唑等不同聚合物骨架结构的阴离子交换膜的制备、性能和应用,同时对具有不同聚合物骨架结构的阴离子交换膜在应用方面存在的问题及应用前景进行了评论和展望。     

An inorganic/organic self-humidifying composite membranes for proton exchange membrane fuel cell application

With an aim to operate the proton exchange membrane fuel cells (PEMFCs) with dry reactants, an inorganic/organic self-humidifying membrane based on sulfonated polyether ether ketone (SPEEK) hybrid with Cs_2.5H_0.5PW₁₂O₄₀ supported Pt catalyst (Pt-Cs2.5 catalyst) has been investigated. The Pt-Cs2.5 catalysts incorporated in the SPEEK matrix provide the site for catalytic recombination of permeable H₂ and O₂ to form water, and meanwhile avoid short circuit through the whole membrane due to the insulated property of Cs_2.5H_0.5PW₁₂O₄₀ support. Furthermore, the Pt-Cs2.5 catalyst can adsorb the water and transfer proton inside the membrane for its hygroscopic and proton-conductive properties. The structure of the SPEEK/Pt-Cs2.5 composite membrane was characterized by XRD, FT-IR, SEM and EDS. Comparison of the physicochemical and electrochemical properties, such as ion exchange capacity (IEC), water uptake and proton conductivity between the plain SPEEK and SPEEK/Pt-Cs2.5 composite membrane were investigated. Additive stability measurements indicated that the Pt-Cs2.5 catalyst showed improved stability in the SPEEK matrix compared to the PTA particle in the SPEEK matrix. Single cell tests employing the SPEEK/Pt-Cs2.5 self-humidifying membrane and the plain SPEEK membrane under wet or dry operation conditions and primary 100 h fuel cell stability measurement were also conducted in the present study.     

Incorporating functionalized silica nanoparticles in polyethersulfone‐based anion exchange nanocomposite membranes

In order to investigate for anion exchange membranes (AEMs) with improved properties, four series of polyethersulfone‐based composite AEMs are fabricated by incorporating pristine and three functionalized silica nanoparticles containing propylamine, trimethylpropylamine, and melamine‐based dendrimer amine groups. The results show that by choosing appropriate functional agent, anion exchange membranes with improved parameters can be achieved. The polymeric matrix of the membranes is synthesized by chloromethylation of polyethersulfone using thionyl chloride followed by amination with trimethylamine (TMA). The effectiveness of chloromethylation process is confirmed by ¹H NMR analysis. The effects of functional groups on characteristic and transport properties of the prepared composite membranes i.e., SEM, IEC, water uptake, porosity transport properties, and conductivity are investigated. The scanning electron microscope images illustrates that the synthesized membranes possess dense structures. Ion exchange capacity (IEC), water uptake, transport properties, and conductivity of the composite membranes are measured. In addition, the morphology and thermal stability are characterized. IECs and ion conductivities of up to 1.45 meq g^?1 and 45.46 mS cm^?1 and moderate transport characteristics are obtained from the modified membranes which confirm that these membranes are appropriate for applying in electro‐membrane processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44596.     

sPEEK based composite membranes for direct ethanol fuel cell applications

In this paper, sulfonated poly(ether ether ketone) (sPEEK) based composite membranes are discussed. The inorganic matrix consisted of silica: Aerosil^® 380, tetraethoxysilane (TEOS), or a combination of both to obtain an interconnected silica network. The ion exchange capacity (IEC) was determined and these values coincided with the predicted IEC values. Uptake in water and 2 M ethanol was performed and an optimum was obtained. TEOS promoted the uptake due to its hydrophilicity. Proton conductivity values of the composite membranes and the polymeric reference were similar, although the IEC was lower. The stability of the composite membranes could be improved by adding an imidazole based functional silane to the composite system. This stability increased with increasing imidazole content resulting in remarkably lower ethanol permeability.     

Novel imidazole‐grafted hybrid anion exchange membranes based on poly(2,6‐dimethyl‐1,4‐phenylene oxide) for fuel cell applications

Novel organic–inorganic hybrid membranes, based on poly(2,6‐dimethyl‐1,4‐phenylene oxide), have been prepared through 1,2‐dimethylimidazole functional groups and double crosslinking agents including 3‐glycidyloxypropyltrimethoxysilane and tetraethyl orthosilicate by sol–gel process for the purpose of improving the conductivity and alkaline resistance. The structure of membranes was characterized using Fourier‐transform infrared spectra, ¹H NMR, and X‐ray diffraction. The physico‐chemical properties of all membranes were shown in ion exchange capacity, water uptake, stability, and conductivity. Membranes with OH^– conductivity up to 0.022 at 25 °C and 0.036 S cm^?1 at 80 °C. Promisingly, the chemical stability of the resulting membranes remains unchanged after storage in 2 mol dm^?3 KOH at 25 °C over at least 10 days. The tensile strength can be higher than 30 MPa, and the elongation at break (Eb) is in the range 6.68–10.84%. Hence, this hybrid membrane can be potentially applied in alkaline fuel cells. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46034.     

Crosslinking of polybenzimidazole membranes by divinylsulfone post‐treatment for high‐temperature proton exchange membrane fuel cell applications

Phosphoric acid‐doped polybenzimidazole (PBI) has been suggested as a promising electrolyte for proton exchange membrane fuel cells operating at temperatures up to 200 °C. This paper describes the development of a crosslinking procedure for PBI membranes by post‐treatment with divinylsulfone. The crosslinking chemistry was studied and optimized on a low‐molecular‐weight model system and the results were used to optimize the crosslinking conditions of PBI membranes. The crosslinked membranes were characterized with respect to chemical and physiochemical properties, showing improved mechanical strength and oxidative stability compared with their linear analogues. Fuel cell tests were further conducted in order to demonstrate the feasibility of the crosslinked membranes. Copyright © 2011 Society of Chemical Industry     

Composite anion exchange membrane for alkaline direct methanol fuel cell: Structural and electrochemical characterization

A copolymer of 4‐vinylpyridine (4‐VP) and styrene was synthesized by radical mass polymerization using 2,2′‐azobisisobutyronitrile as initiator. An insoluble (linear) pyridinium‐type polymer was prepared by the reaction of P (4VP–St) with 1‐bromooctane. An anion exchange membrane was prepared using a composite of pyridinium‐type polymer and a fibrous woven structure for use in electrochemistry. The composite membrane was characterized by X‐ray diffraction, tensile strength, scanning electron microscopy, and electrochemistry measurements. The experimental results showed that the fibrous woven product had improved the tensile strength more than had the membrane made of a pyridinium‐type polymer alone. The composite membrane was used in alkaline fuel cells, and its properties were measured by electrochemical analysis. The ionic conductivity of the membrane was acceptable, but its performance as a direct methanol fuel cell (DMFC) was not. The primary reason for this was analyzed, and research is ongoing, with analysis to be discussed in later reports. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2248–2251, 2006     

Preparation and properties of chitosan/acidified attapulgite composite proton exchange membranes for fuel cell applications

A composite proton exchange membrane chitosan (CS)/attapulgite (ATP) was prepared with the organic–inorganic compounding of ATP and CS. The composite membranes were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). The mechanical properties, thermal stability, water uptake, and proton conductivity of the composite membranes were fully investigated. The composite membranes exhibited an enhanced mechanical property, dimensional and thermal stability compared to CS membrane, owing to the interface interaction between ATP and CS. The maximum tensile strength of 53.1 MPa and decomposition temperature of 223.4°C was obtained, respectively. More importantly, the proton conductivity of the composite membrane is also enhanced, the composite membrane with 4 wt% ATP content (CS/ATP-4) exhibited the highest proton conductivity of 26.2 mS cm⁻¹ at 80°C with 100% relative humidity, which is 25.1% higher than pure CS membrane. These results may explore a simple and green strategy to prepare CS-based PEMs, which have a great potential in the application of proton exchange membrane fuel cells.     

Preparation of proton exchange membranes based on crosslinked polytetrafluoroethylene for fuel cell applications

We prepared proton exchange membranes by the γ-ray-induced post grafting of styrene into crosslinked polytetrafluoroethylene (PTFE) films and subsequent sulfonation. The degree of grafting was controlled in the range of 7-75% by the crosslinking density of the PTFE matrix as well as the grafting conditions. Under our preparation conditions, the films at the grafting yield of ≥30% were found to produce ion exchange membranes with a homogeneous distribution of sulfonic acid groups. The resulting membranes showed a large ion exchange capacity up to 2.9 meq g⁻¹, which exceeded the performance of commercially available perfluorosulfonic acid films such as Nafion; nevertheless, they appeared to be dimensionally stable in water. These should undoubtedly result from the use of the crosslinked PTFE films as graft substrates and make our ion exchange membranes promising for applications to polymer electrolyte fuel cells.     

Novel crosslinked AB‐type polyphenylquinoxaline membranes for high‐temperature proton exchange membrane fuel cells

AB‐type polyphenylquinoxaline (ABPPQ) membranes exhibit great mechanical properties and thermal properties for high‐temperature proton exchange membranes (PEMs). However, they dissolve in high‐concentration phosphoric acid (PA) during acid doping. In order to improve the PA resistant of ABPPQ, crosslinked ABPPQ membranes were prepared using sulfuric acid. The crosslinked ABPPQ membranes showed high PA resistance. The acid content of PA‐doped membranes decreased slightly with crosslinking, but the crosslinked polyphenylquinoxaline (CPPQ)‐20 membrane could reach 2.5 × 10^?2 S/cm proton conductivity at 160°C. Membrane electrode assemblies were fabricated with an active area of 4 cm² and Pt loading of 1 mg/cm². A startup and shutdown test (operated at 150°C with 0.2 A/cm² for 12 h and then 12 h off at room temperature) and a 30‐day long‐term durability test (150°C with 0.2 A/cm²) were conducted. In the startup and shutdown test, the crosslinked membranes showed a low open‐circuit voltage decay rate of 0.15 mV/h. In the 30‐day long‐term durability test, the voltage decay rate was 0.039 mV/h. In both tests, the crosslinked membranes showed a stable performance. Therefore, the crosslinked ABPPQ membranes can be regarded as a novel material for high‐temperature PEM fuel cells. POLYM. ENG. SCI., 59:2169–2173, 2019. © 2019 Society of Plastics Engineers     

燃料电池用碱性膜材料的研究进展

碱性膜直接甲醇燃料电池因为结合了质子交换膜燃料电池和液体碱燃料电池的优点而产生自身独特的性质,使其可以在一定程度上弥补质子交换膜燃料电池以及液体碱燃料电池的缺点而尤其引人关注。其中碱性膜电解质为碱性膜燃料电池的核心组件,其性能直接关系到燃料电池的性能及寿命。截至目前,关于碱性膜材料的制备及应用方面的报道较多,涉及的碱性膜电解质的种类也较多。本文以燃料电池用碱性膜电解质为综述内容,对国内外关于碱性膜电解质的研究报道进行系统的梳理和介绍。     

基于微孔聚四氟乙烯的复合质子交换膜

研究了基于微孔聚四氟乙烯（PTFE）的复合方式,通过将自制ABPSH40树脂——N,N-二甲基乙酰胺溶液流延在用液相介质表面处理法改性过的聚四氟乙烯微孔膜表面上,制得了均匀的ABPSH40/PTFE 增强复合质子交换膜。采用扫描电镜（SEM）观察复合膜的表面及断面形态,采用气相色谱仪（GC）测定了复合膜的甲醇渗透性,利用交流阻抗（AC）测定了膜的质子传导率。结果表明,ABPSH40树脂在复合膜内分布均匀,而且PTFE膜微孔填堵充分;复合膜具有优越的尺寸稳定性,较低的甲醇渗透率和接近Nafion膜的质子传导率,和ABPSH40均质膜进行比较后的优点明显。ABPSH40/PTFE 增强复合质子交换膜可望成为一种直接甲醇燃料电池用质子交换膜。     

Poly (ether ether ketone ketone) based imidazolium as anion exchange membranes for alkaline fuel cells

An imidazolium functionalized poly (ether ether ketone ketone) (PEEKK-DImOH) anion exchange membrane (AEM) readily soluble in certain low-boiling-point solvents (isopropanol) is prepared. The solubility results are consistent with the results of molecular dynamics simulations. By varying the chloromethylation reaction temperature or concentrated sulfuric acid concentration of PEEKK, the degrees of chloromethylation of PEEKK are changed from 54% to 92%, the corresponding PEEKK-DImOH AEMs with the ion exchange capacities (IECs) of 1.14-1.65 mmol·g^-1. The PEEKK-DImOH 92% AEM shows high hydroxide conductivity (31 mS·cm^-1), suitable water uptake (94%) and acceptable swelling ratio (39%) at 60℃. In addition, the PEEKK-DImOH AEMs possess good thermal and alkaline stability. The maximum power density (46.16 mW·cm^-2) of fuel cell prepared with PEEKK-DImOH 92% AEM as exchange membrane and ionomer is much higher than that with commercial AHA membranes. All the above results indicate that the PEEKK used in this study is a promising AEM matrix material for alkaline fuel cells.     

Aligned electrospun sulfonated polyetheretherketone nanofiber based proton exchange membranes for fuel cell applications

In this study, electrospinning of sulfonated poly(ether ether ketone) (SPEEK) at different degrees of sulfonation (DS) was investigated. The polymer solution concentration of 22 wt% was obtained to collect smooth fiber in nanoscale range of 112 to 131 nm at various conditions. SEM observations of SPEEK nanofibers showed the decrease of diameter with increasing DS from 74% to 81%, mainly due to the increase of electrical conductivity of polymer solution at higher DS. The increase of collecting speed from 20 to 305 m/min decreased the diameter of nanofibers slightly and improved their alignment. The presence of SO₃H groups in collected nanofibers was demonstrated with FT‐IR analysis. WAXD patterns of SPEEK nanofibers indicated featureless amorphous peak with no crystalline regions that was broaden at higher DS and aligned nanofibers. The electrochemical impedance spectroscopy of SPEEK nanofibers showed the through‐plane proton conductivity of fully hydrated nanofibrous membranes measured at room temperature were improved with DS. The proton conductivity of randomly oriented and aligned nanofibers were measured from 0.0098 to 0.0722 S/cm and from 0.0592 to 0.0907 S/cm, respectively. Aligned nanofibers exhibited more proton conductivity than randomly collected nanofibers. POLYM. ENG. SCI., 57:789–796, 2017. © 2016 Society of Plastics Engineers     

质子交换膜燃料电池用全氟磺酸复合膜性能研究

以醇和水为混合溶剂,在高温高压下制得了全氟磺酸树脂回收液,并用FYPFSA溶液改善了回收液的成膜性能,然后以PTFE多孔膜为增强材料,制成全氟磺酸/PTFE复合膜用于质子交换膜燃料电池,对复合膜的物理化学性能和电化学性能进行了测定.在41.5℃、p(H2)=0.03 MPa、P(O2)=0.2 MPa条件下用复合膜CM1组装的电池最大功率密度达到0.4 W/cm2.     

A morpholinium-functionalized poly(ether sulfone) as a novel anion exchange membrane for alkaline fuel cell

A methyl morpholinium-functionalized poly(ether sulfone) (MM-PES) copolymer was prepared as a novel anion exchange membrane. The MM-PES polymer was synthesized by polycondensation between the morpholine-containing hydroquinone and bisphenol A with bis(4-fluorophenyl)sulfone, followed by methylation of the morpholine group. The membrane obtained from MM-PES showed an IEC of 0.90 meq/g with high hydroxide conductivity of 1.6 × 10^?2 S/cm at r.t. and 7.9 × 10^?2 S/cm at 80 °C. The methyl morpholinium-functionalized PES membrane also displayed good hydrolytic, thermal, mechanical and chemical stabilities.     

Polysulfone‐based anion exchange polymers for catalyst binders in alkaline electrolyzers

The preparation of quaternized bisphenol A polysulfone (PSf) by chloromethylation and quaternization with trimethylamine (TMA), 1,4‐diazabicyclo[2.2.2]octane (DABCO), 1‐methylimidazole (MI), or 1,2‐dimethylimidazole (DMI) is described. While the ion‐exchange capacities (IECs) of MI or DMI quaternized PSf significantly decrease in concentrated KOH solutions at 60°C, the IECs of TMA or DABCO quaternized PSf are not much affected, but the membranes of these polymers become brittle. TMA quaternized PSf (IEC = 1.21 meq/g; IC = 2.45 S/m) and DABCO quaternized PSf (IEC = 1.09 meq/g; IC = 2.49 S/m) were used to bind a NiCo₂O₄ spinel electrocatalyst on the anode of Ni foam. Both the quaternized PSfs were quite effective in water electrolysis when used as binders, but not more effective than PTFE when rear sides of electrodes were fed with 10 wt % aqueous KOH solution. For long‐term electrolysis, binders based on more stable anion‐conductive polymers should be developed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42581.     

Quaternized poly(phenylene oxide) anion exchange membrane for alkaline direct methanol fuel cells in KOH‐free media

A series of anion exchange membrane (AEM) electrolytes with quaternary ammonium moiety are fabricated from poly (phenylene oxide) for its application in alkaline direct methanol fuel cells (ADMFCs). In the first step, poly(phenylene oxide) (PPO) is successfully chloromethylated by substituting chloromethyl groups in the aryl position of polymer. In the second step, the chloromethylated PPO (CPPO) is further homogeneously quaternized and ion‐exchanged to form an AEM. From the second step, series of AEMs are prepared by changing the mole ratio of amine in relation to CPPO. The presence of quaternary ammonium group in the membrane was confirmed by elemental analysis. The fabricated membranes are subjected to cell polarization studies in ADMFCs, wherein quaternized poly(2,6‐dimethyl‐1,4‐phenylene oxide) (CPPO:amine of 1:8) membrane exhibits higher peak power density of 3.5 mW cm^?2 when compared with the other ratios of CPPO:amine in the absence of KOH solution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43693.