Solid Alkaline Fuel Cells Research Articles

Thermally crosslinked and quaternized polybenzimidazole ionomer binders for solid alkaline fuel cells

A novel anion-conducting ionomer binder, quaternized polybenzimidazoles (QPBIs) with 4-methyl-4-glycidylmorpholin-4-ium chloride (MGMC) in the main-chain and/or in the side group were synthesized for solid alkaline fuel cells (SAFCs). Crosslinking of the polybenzimidazole derivatives using a crosslinker containing epoxy groups formed ionomer binder in electrodes, and the crosslinked QPBIs showed better mechanical stability than non-crosslinked QPBIs. During the electrode drying process, on-site crosslinking was introduced to form thermally crosslinked ionomer binder in catalyst layers. A bench-scale SAFC with the crosslinked QPBI (CQPBI) containing 35 wt% of ionomer binder showed higher peak power density (35.3 mW cm−2) than the SAFC with 2,2′(m-phenylene)-5,5′bibenzimidazole (m-PBI) with 35 wt% of ionomer binder (20.9 mW cm−2). The membrane-electrode assembly (MEA) with CQPBI (35 wt% binder) showed two times higher chemical stability than that with m-PBI (35 wt% of ionomer binder) in load cell tests.

KOH-doped Porous Polybenzimidazole Membranes for Solid Alkaline Fuel Cells

In this study the preparation and properties of potassium hydroxide-doped meta-polybenzimidazole membranes with 20–30 μm thickness are reported as anion conducting polymer electrolyte for application in fuel cells. Dibutyl phthalate as porogen forms an asymmetrically porous structure of membranes along thickness direction. One side of the membranes has a dense skin layer surface with 1.5–15 μm and the other side of the membranes has a porous one. It demonstrated that ion conductivity of the potassium hydroxide-doped porous membrane with the porogen content of 47 wt.% (0.090 S cm−1), is 1.4 times higher than the potassium hydroxide-doped dense membrane (0.065 S cm−1). This is because the porous membrane allows 1.4 times higher potassium hydroxide uptake than dense membranes. Tensile strength and elongation studies confirm that doping by simply immersing membranes in potassium hydroxide solutions was sufficient to fill in the inner pores. The membrane-electrode assembly using the asymmetrically porous membrane with 1.4 times higher ionic conductivity than the dense non-doped polybenzimidazole (mPBI) membrane showed 1.25 times higher peak power density.

Study on Synthesis and Characterization of Composite Anion Exchange Membrane Based on poly(styrene-co-vinylbenzyl ammonium hydroxide) and poly(vinyl alcohol)

In this study, poly(styrene-co-vinyl benzyl trimethyl ammonium chloride) with different styrene to vinyl benzyl chloride ratio (3:1, 1:1, 1:2) have been synthesized. The formation ofproducts was confirmed by Fourier transform infrared spectrophotometry (FTIR) and nuclear magnetic resonance spectra (1H NMR). Then, anion exchange membranes were prepared by combination of poly(styrene-co-vinyl benzyl trimethyl ammonium hydroxide) and poly (vinyl alcohol) The obtained membranes were evaluated for their own conductivity, anion exchange capacity, and thermal decomposition. The results showed that the anion exchange membrane produced from copolymer with styrene to vinyl benzyl chloride ratio 1: 2 exhibited good hydroxide conductivity of 7 mS/cm, ion exchange capacity was 0.65mmol/g and stability to 200oC.
 Keywords
 Membrane, poly(vinyl alcohol), copolymer, conductivity, fuel cell.
 References
 [1] D. J. Kim, C. H. Park, S. Y. Nam, Characterization of a soluble poly(ether ether ketone) anion exchange membrane for fuel cell application, Int. J. Hydrogen Energy 41 (2016) 7649-7658. https:// doi.org/10.1016/j. ijhydene.2015.12.088[2] J. Fu, J. Qiao, H. Lv, J. Ma, X.-Z. Yuan, H. Wang, Alkali doped poly(vinyl alcohol) (PVA) for anion-exchange membrane fuel cells - Ionic conductivity, chemical stability and FT-IR characterizations, Alkaline Electrochem. Power Sources 25 (2010) 15–23. http://doi.rog/10.1149/ 1.3315169[3] D. L. Zugic, I. M. Perovic, V. M. Nikolic, S. L. Maslovara, M. P. Marceta Kaninski, Enhanced Performance of the Solid Alkaline Fuel Cell Using PVA-KOH Membrane, Int. J. Electrochem. Sci. 8 (2013) 949-957. [4] Jikihara, R. Ohashi, Y. Kakihana, M. Higa, and K. Kobayashi, Electrodialytic transport properties of anion-exchange membranes prepared from poly(vinyl alcohol) and poly(vinyl alcohol-co-methacryloyl aminopropyl trimethyl ammonium chloride), Membranes (Basel) 3 (2013) 1-15. http: //doi.rog/10.3390/membranes3010001[5] S. Vengatesan, S. Santhi, S. Jeevanantham, G. Sozhan, Quaternized poly(styrene-co-vynylbenzyl choloride) anion exchange membranes for alkaline water electrolysers, Journal of Power Sources 84 (2015) 361-368. https://doi.org/10.1016/j.jpowsour. 2015.02.118[6] L. E. Shmukler, N. V. Thuc, and L. P. Safonova, Conductivity and thermal stability of proton-conducting electrolytes at confined geometry of polymeric gel, Ionics 19 (2013) 701-707. https:// doi.org/10.1007/s11581-012-0800-2[7] D//A. Lewandowski, K. Skorupska, J. Malinska, Novel poly(vinyl alcohol)–KOH–H2O alkaline polymer electrolyte, Solid State Ionics 133 (2000) 265-271. https://doi.org/10.1016/S0167-2738(00) 00733-5 [8] Jun F, Y. Wu, Y. Zhang, M. Lyu, J. Zhao, Novel anion exchange membranes based on pyridinium groups and fluoroacrylate for alkaline anion exchange membrane fuel cells, Int. J. Hydrogen Energy 40 (2015) 12392-12399. https://doi.org/10. 1016/j.ijhydene.2015.07.074[9] Géraldine M, M. Wessling, K. Nijmeijer Anion exchange membranes for alkaline fuel cells: A review, Journal of Membrane Science, 377(2011) 1-35. https://doi.org/10.1016/j.memsci.2011.04.043.
 

Highly stable membrane–electrode assembly using ether-linkage-free spirobifluorene-based aromatic polyelectrolytes for direct formate solid alkaline fuel cells

The low stability of membrane–electrode assemblies (MEAs) in solid alkaline fuel cells (SAFCs) operating at high temperatures and in highly alkaline conditions is a critical issue. In this study, we developed a membrane–electrode assembly (MEA) using highly durable ether-linkage-free aromatic polyelectrolytes with a three-dimensionally twisted spirobifluorene (SBF) backbone for direct formate SAFCs (DF-SAFCs). Here, the SBF-based polyelectrolytes were employed as an ionomer for catalyst layers and as a protective thin layer (less than 1 μm in thickness) for the surface coating on a conventional anion-conducting pore-filling membrane. The simple method of the coating of durable polyelectrolyte layers on the membrane surfaces provided high chemical stability of the membrane against both alkaline and OH radicals, as well as a reduced permeability of formate through the membrane, while maintaining a low water uptake and high ionic conductivity. The MEA using these materials achieved a high performance with a maximum power density of 210 mW cm−2 in DF-SAFCs. More importantly, this study, for the first time, demonstrated the high stability of the MEA during long-term DF-SAFC operation (approximately 50 h in one week) in highly alkaline conditions and at a high temperature of 80 °C.

Poly (Ether Ether Ketone) Based Anion Exchange Membrane for Solid Alkaline Fuel Cell: A Review

Solid alkaline fuel cell is employed by polymer anion exchange membrane (AEM) that is permeable to hydroxide ion. A number of polymers have been proposed for AEM which include polysulfone (PSF), poly (phenylene oxide) (PPO), and poly (ether ether ketone) (PEEK). The purpose of this paper was to conduct a critical review on the development of PEEK polymer as AEM, particularly in terms of the fabrication methods, cationic functionalized group reagent, and the effect of fller addition on membrane properties. PEEK is a thermoplastics polymer that possesses superior mechanical, thermal, and chemical stability. The basic development of PEEK-based AEM involves the process of attaching the cationic functionalized group, namely quaternary ammonium (QA), quaternary phosphonium (QP), and imidazolium (Im) groups onto the PEEK backbone. Up to the recent time, the chloromethylation-functionalization and acid-base blending methods are among the commonly used fabrication methods in developing PEEK-based AEM. The increase in the degree of functionalization (DF) caused the basic PEEK-AEM, namely QA-PEEK, QP-PEEK, and Im-PEEK to exhibit high hydroxide conductivity apart from the degradation in alkaline stability, mechanical property, and dimensional stability. The modifcation of the membranes performed through the addition of fller or ionic-crosslink between acid and base may improve the anion conduction pathway, alkaline stability, mechanical property and water retention property of the membrane due to the increase of the DF.

Development of Highly Conductive and Highly Durable All-Aromatic Anion Exchange Membranes By Using Thermally Convertible Precursor Polymer

Solid Alkaline Fuel Cells (SAFCs) using Anion Exchange Membranes (AEMs) attracts increasing attention for next-generation fuel cell technology. SAFCs have many advantages over proton exchange membrane fuel cell such as variable choice of metal electrode catalyst and fuels. However, the commercialization of SAFCs is limited due to the lack of high-performance AEMs. Commonly, AEMs have low ionic conductivity and poor durability in alkaline medium. In this study, we developed a novel AEM comprises of wholly aromatic, anthracene-based, backbone as a chemically durable membrane. Commonly, such kind of polymers exhibits very low solubility in common organic solvent due toπ-πstacking. Thus the processability into a membrane is very difficult. Our unique molecular design is employing bulky Thermal Leaving Group (TLG) on the precursor polymer allowing this polymer to be cast as a film due to high solubility (>300 mg/ml). Then, TLG on the membrane film was removed by performing retro Diels-Alder reaction1,2 in the solid state to obtain a wholly aromatic membrane (figure 1 (a)). The precursor polymer was obtained by Suzuki-Miyaura coupling of the monomers. The methyl group of the resulting polymer was converted to benzyl bromide and finally to quaternary trimethylammonium bromide to afford the target precursor polymer (TPP). The polymer structure and molecular weight were analyzed by 1H-NMR and GPC. Ion exchange capacity (IEC) was determined by titration. The in-plane ionic conductivity of the membrane is evaluated by AC impedance method. Stability test in hot alkaline solution and Fenton solution was performed to check the chemical durability of the membrane. Molecular weight and IEC of synthesized TPP are 13,000 g/mol and IEC 2.49, respectively. Target polymer (TP) membrane was then obtained by just heating TPP membrane and removing TLG. The best heating temperature was determined to be 180 oC by TGA-MS analysis. IEC of the membrane has increased to 3.16 after thermal conversion. Despite higher IEC value, water uptake of TP membrane was lower than TPP membrane probably due to the strong intermolecular interaction of TP membrane. Therefore, TP membrane keeps higher IEC even after water uptake and this may result in high anion conductivity. Figure 1 (b) shows the ionic conductivity of TP membrane before and after the durability test. The membrane kept initial HCO3 - conductivity even after exposed to a very harsh alkaline solution (8M NaOH for 21 days at 80 oC) and Fenton solution (H2O2 3 wt%, FeSO4 3 ppm at 60 oC for 8 hours). This is a solid proof that the TP membrane has both high durability and high conductivity, meeting for SAFC application. These findings suggest that the use of TLG on polymer backbone allow development of new design concepts for highly-durable and highly conductive AEMs.

Highly-Durable Membrane Electrode Assembly for Direct Formate Solid Alkaline Fuel Cells

Solid alkaline fuel cells (SAFCs) have attracted much attention as next-generation energy conversion electrochemical devices. Despite numerous advantages of SAFCs including the usages of various type catalysts and liquid fuels with high energy density, the practical applications of these devices are limited because of the drastic decrease in the cell performance during the high temperature operation under alkaline condition. This low performance of the device is mainly attributed to the severe degradation of membrane-electrode assembly (MEA). Therefore, the development of a durable and stable MEA is critical to improve the cell performances and stabilities in this system. Here we report the development of highly-durable MEA using a new carbon-free cathode catalyst and an aromatic polyelectrolytes without an ether linkage. As shown in Fig. 1A-a, the carbon-free catalyst consists of a nanosized beaded network formed by the connection of Pt–Fe nanoparticles.[1–3] The beaded metal network is electrically conductive, enabling the removal of carbon supports from catalyst layer. Hence, carbon corrosion problems can be avoided, leading to high durability against the cyclic start-stop operation of the system. We successfully demonstrated the high durability of this carbon-free catalyst in alkaline electrolyte solution. In addition, the specific activity of a connected Pt–Fe catalyst for oxygen-reduction-reaction (ORR) is about five times higher than that of a commercial Pt-nanoparticle catalyst supported on carbon black. Fig. 1A-b represents the chemical structure of new spirobifluorene-based aromatic ionomer with no ether-linkage. This anion-conductive ionomer exhibited high alkaline and oxidative durability because the backbone did not contain ether linkages, heteroatoms, and benzylic C–H bonds. It was also demonstrated that the thin-layer coating (< 1 μm) of spirobifluorene-based ionomer on the anion-exchange membrane (Fig. 1A-c) improved alkaline and oxidative stability, and suppressed the permeability of potassium formate (HCOOK) as fuel. We fabricated the MEA using the in-house made durable catalyst and membrane material, i.e., the carbon-free connected Pt–Fe catalyst, spirobifluorene-based ionomer, and anion conductive pore-filling membrane with durable thin layer. The in-house made MEA, operated at a high temperature of 80 °C, exhibited high power density of 220 mW cm−2 and high open circuit voltage of about 1.0 V (Fig. 1B), here, a mixture of aqueous solutions of 4M HCOOK and 2 M KOH was used as the fuel. Further, more importantly, the high performance of the MEA retained even after the operation at 80 °C and 0.2 A cm−2 for 150 h. Therefore, for the first time, we demonstrated a highly durable and stable MEA in alkaline medium for the direct formate SAFCs. [1] T. Tamaki, H. Kuroki, S. Ogura, T. Fuchigami, Y. Kitamoto, and T. Yamaguchi, Energy Environ. Sci., 8, 3545–3549 (2015). [2] H. Kuroki, T. Tamaki, and T. Yamaguchi, J. Electrochem. Soc., 163(8), F927–F932 (2016). [3] H. Kuroki, T. Tamaki, M. Matsumoto, M. Arao, Y. Takahashi, H. Imai, Y. Kitamoto, and T. Yamaguchi, ACS Appl. Energy Mater., 1(2), 324–330 (2018). Figure 1

Preparation and Characterizations of Anion Conducting Ionomer Binder Solutions for Solid Alkaline Fuel Cells

Compared to fuel cells using proton exchangeable polymers, the direction of ion movement in the fuel cells using anion conducting polymer membranes shown in Figure 1 is opposite which is from cathode to anode. The hydroxyl ion movement mitigates overpotential for oxygen reduction reaction as well as water flooding at cathode. In addition, they overcome the disadvantages of alkaline fuel cells such as formation of carbonate precipitates, leakage of liquid KOH electrolyte, system complexity and so on by using solid electrolytes. Anion conducting ionomers are the polymers where anion exchangeable fixed groups, e.g., quaternary ammonium groups, are covalently attached to main backbones. It conducts the selective movement of anions which is allowed to be transported inside free volume of wet polymers. Much efforts are devoted to the development of anion conducting membranes as electrolytes of the fuel cell, but few researches on ionomer binder solutions for preparation of electrodes of membrane-electrode assemblies were carried out due to the technical difficulty in dispersing the polymers in various solvent systems. In this study, poly(phenylene oxide) (PPO) were brominated and in-situ quaternized by trimethyl ammonium during membrane casting. Once it was cast, it was hardly dispersed in any solvent system. Thus, the polymer was frozen by aqueous nitrogen and was ground by a blade-type grinder. Upon grinding time, the final forms were powders with different size of particle. The powder was used to prepare ionomer binder solutions, and the solutions (or dispersions) were characterized in terms of ion conductivity, ion exchange capacity, FT-IR, dynamic light scattering. In addition, the performance of membrane-electrode assemblies with the content of the ionomer with respect to I-V polarization, cyclic voltammetry, and impedance. Acknowledgment This work was supported by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning(KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20153030031720).

고분자 분쇄 기술을 활용한 고체 알칼리연료전지용 이오노머 바인더 용액 개발

In this study, an anion-exchange ionomer solution was prepared by grinding poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) in liquid nitrogen for solid alkaline fuel cells (SAFCs). Type of quaternized PPO (QPPO) solutions was controlled by grinding time. The ionomer binder solutions were characterized in terms of dispersity, particle size, and electrochemical properties. As a result, ionomer binder solutions using grinded polymer showed higher dispersion and smaller particle size distribution than that using non-grinded polymer. The highest ionic conductivity and IEC of the membrane recast by using BPPO-G120s were and , respectively.

Development of anion-conducting ionomer binder solutions for electrodes of solid alkaline fuel cells.

For solid alkaline fuel cell applications, membrane-electrode assemblies (MEAs) should be prepared. Thus, in this study, anion-conducting ionomer binder was prepared for electrodes of MEAs. Specifically, we synthesized water soluble anionic binder solutions based on quaternized chitosan derivatives (QCDs) and cross-linked QCDs and prepared a novel electrode. The electrochemical and physicochemical properties of ionomer binder and electrode were investigated by FT-IR, NMR and ionic conductivity. The ionic conductivity of these cross-linked QCDs was 9.7 x 10(-3) S cm(-1) in deionized water at room temperature. The membrane electrode assemblies (MEAs) were prepared by a spray method and were investigated in terms of cyclic voltammetry, impedance and fuel cell performance. The MEA with the 35 wt% QCD ionomer showed the highest performance and confirmed the successful formation of ionomer binder at the electrode of the MEA by the on-site crosslinking reaction.

Guanidine functionalized radiation induced grafted anion-exchange membranes for solid alkaline fuel cells

Alkaline anion-exchange membranes (AAEMs) for solid alkaline fuel cells (SAFC) application were successfully prepared by radiation induced grafting of Vinyl benzyl chloride onto ultra-high molecular weight polyethylene powder (UHMWPE), followed by film fabrication by melt pressing and quaternization with a Guanidine derivative, 1,1,3,3-tetramethyl-2-n-butylguanidine (TMBG). The chemical structures of the resulting AAEMs were examined by Fourier transform infrared, which showed that the grafted membranes were successfully functionalized by modified guanidine. The performance of the AEMs, including ion exchange capacity, water uptake, in-plane swelling, methanol uptake, methanol permeability, and hydroxide ion conductivity were investigated. Thermal analysis showed that the Guanidine-based AAEMs comprises better thermal stability. The AAEMs membrane exhibited a maximum ionic conductivity of 27.7 mS cm−1 at 90 °C. Methanol permeability is found to be in the order of 10−9 cm2 s−1, which is significantly lower than that of Nafion®. The membranes have useful properties as an anion exchange membranes suitable for alkaline fuel cells.

Enhanced Performance of the Solid Alkaline Fuel Cell Using PVA-KOH Membrane

Enhanced Performance of the Solid Alkaline Fuel Cell Using PVA-KOH Membrane

A Novel Composite Membrane from QPSU and SiO2 for Solid Alkaline Fuel Cell Applications

The goal of this work is to develop a novel composite membrane from quaternized polysulfone (QPSU) and silica (SiO2), to fabricate alkaline membrane electrode assemblies (MEAs) and to subsequently test the MEAs in 5 cm × 5 cm single cell configuration using Pt/C and Ag/C as anode and cathode catalysts, respectively. The composite membranes were characterized in terms of water absorption, ion exchange capacity and ionic conductivity. The physicochemical studies Fourier transform infra red (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) studies, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and universal testing machine (UTM) were used to investigate the relation between the structure and performance of the composite membranes. The results show that the SiO2 was compatible with the QPSU membrane. The thermal stability and ionic conductivity of the QPSU/SiO2 composite membranes were higher than that of quaternized polysulfone (QPSU) membrane. The maximum performance was achieved for 10 wt.% SiO2 with power density of 149.6 mW/cm2 at current density of 440 mA/cm2.

Anion Conducting Pore-Filling Membranes for Solid Alkaline Fuel Cells

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Water Transport Properties of Plasma-Modified Commercial Anion-Exchange Membrane for Solid Alkaline Fuel Cells

In the field of low-temperature fuel cells, solid alkaline membrane fuel cells (SAMFCs) appear to be a very promising new fuel cell technology. Nevertheless, commercial hydroxyl-exchange membranes suitable for SAMFCs suffer from some limitations, especially low retention to water at the cathode (where water is required to be reactive in the electrochemical reaction), which weakens fuel cell performances. In this study, the commercial Morgan ADP membrane by Solvay has been modified on the surface by plasma processes using argon or argon/triallylamine as gaseous phases. Plasma-treated and untreated membranes have been characterized in terms of water sorption and diffusion properties performing water vapor sorption measurements. Analysis of sorption isotherms and related modeling from Park model has shown that plasma treatments induce a decrease in water sorption and diffusion abilities without qualitatively affecting the water transport properties. Plasma modification from triallylamine leading to the depos...

Development of Water Soluble Anionic Binder Solutions for Solid Alkaline Fuel Cells

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P1.035] New Copolymers for Solid Alkaline Fuel Cell Membranes

P1.035] New Copolymers for Solid Alkaline Fuel Cell Membranes

Performance comparison of modified poly(vinyl alcohol) based membranes in alkaline fuel cells

There are several problems which are holding back the use of fuel cells. The utilization of fuel cells depends on the start-up costs which are very high due to the use of expensive materials for their construction. In that respect, we describe a cost-effective alkaline fuel cell (AFC) that uses solid, polymer based, membrane instead of conventionaly used, highly concentrated, corrosive, liquid alkaline electrolyte. This approach to AFC is potentially the basis of a simple, low-cost system, that can solve one of the problems of the highly-efficient and environment-friendly AFC. The focus of this paper are low cost composite alkaline membranes, based on poly(vinyl alcohol) (PVA). The PVA matrix is made by solution cast method and gamma irradiation crosslinking. Three different types of membranes are obtained in this manner – plain PVA membrane, PVA membrane cross-linked using gamma irradiation (γ-PVA) and composite PVA membrane doped with Mo (PVA-Mo). These membranes are immersed in the alkaline solution and investigated as anion exchange membranes. The performance of the solid alkaline fuel cells (SAFCs) containing these PVA membranes has been studied under hydrogen and oxygen gas flow on the Pt/C catalyst. Both, γ-PVA and PVA-Mo membranes are modified to absorb larger amounts of alkaline solution than the PVA membrane, thus greatly improving the performance of the SAFC, in terms of output power. This is clearly indicated in the polarisation curves. The electrochemical impedance spectroscopy measurements during the SAFC operation were also performed to give better insight in the effect observed. Investigation presented in this paper clearly indicates that solid alkaline PVA membranes can be used for the construction of the SAFCs.

Function of Each Element in Fe-Co-Ni/C Anode Catalyst on the Performance of Solid Alkaline Fuel Cell

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Performance of Solid Alkaline Fuel Cells Employing Layered Perovskite-Type Oxides as Electrolyte

Layered perovskite-type oxides were characterized by electrochemical measurement. Five kinds of perovskite oxides (LaSr3Fe3O10, NaLaTiO4, Sr4Co1.6Ti1.4O8(OH)2⋅xH2O, RbLaNb2O7 and LaFeO3) were used as electrolyte of fuel cells. Every perovskite oxide could generate current and high open circuit voltage (>0.8 V). The results were attributed to hydroxide ion (OH-) conduction resulting from reduction and H2O treatments. This hypothesis suggests that the possibility of a new alkaline fuel cell by using layered perovskite as electrolyte.