High-performance polymer electrolyte membranes incorporated with 2D silica nanosheets in high-temperature proton exchange membrane fuel cells

Silica nanosheets(SN)derived from natural vermiculite(Verm)were successfully incorporated into polyethersulfone-polyvinylpyrrolidone(PES-PVP)polymer to fabricate high-temperature proton exchange membranes(HT-PEMs).The content of SN filler was varied(0.1-0.75 wt%)to study its influence on proton conductivity,power density and durability.Benefiting from the hydroxyl groups of SN that enable the formation of additional proton-transferring pathways,the inorganic-organic membrane displayed enhanced proton conductivity of 48.2 mS/cm and power density of 495 mW/cm² at 150℃ without humidification when the content of SN is 0.25 wt%.Furthermore,exfoliated SN(E-SN)and sulfonated SN(S-SN),which were fabricated by a liquid-phase exfoliation method and silane condensation,respectively,were embedded in PES-PVP polymer matrix by a simple blending method.Due to the significant contribution from sulfonic groups in S-SN,the membrane with 0.25 wt%S-SN reached the highest proton conductivity of51.5 mS/cm and peak power density of 546 mW/cm² at150℃,48%higher than the pristine PES-PVP membranes.Compared to unaltered PES-PVP membrane,SN added hybrid composite membrane demonstrated excellent durability for the fuel cell at 150℃.Using a facile method to prepare 2D SN from natural clay minerals,the strategy of exfoliation and functionalization of SN can be potentially used in the production of HT-PEMs.     

Promotion of proton conduction in polymer electrolyte membranes by 1H-1,2,3-triazole

We report 1H-1,2,3-triazole as an active group to dramatically enhance proton conduction in a polymer electrolyte membrane (PEM). The conductivities of a poly(4-vinyl-1H-1,2,3-triazole) membrane without any acidic dopants are about 105 times greater than those of poly(4-vinylimidazole) in dry air at 50-150 degrees C. Polymers with groups promoting proton conduction attached to the backbone have great potential to offer excellent mechanical properties and long-term stability. Further, 1H-1,2,3-triazole and PEMs containing 1H-1,2,3-triazole are stable in a wide potential range, implying excellent electrochemical stability under fuel cell operating conditions.     

Synthesis of anion conducting polymer electrolyte membranes by Pd-Catalyzed Buchwald-Hartwig Amination coupling reaction

A novel aryl bromine bearing polymer was synthesized by Friedel-Crafts polycondensation. This precursor polymer substrate was used for C–N coupling via Buchwald-Hartwig amination to incorporate 9 examples of aryl amines into the polymer chains with high conversions (80–100%). Two aminated polymers were subsequently quaternized to give anion conducting polymers. These quaternary ammonium polymers show promising electrochemical membrane property because of their ability to transport mobile anions through the material while being electrically insulating. Membrane characteristics crucial to high electrochemical performance including ion exchange capacity, anion conductivity, water uptake, swelling ratio, and alkaline stability were evaluated.     

Recent advances in phosphoric acid-based membranes for high-temperature proton exchange membrane fuel cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are pursued worldwide as effi-cient energy conversion devices.Great efforts have been made in t...     

On the development of proton conducting polymer membranes for hydrogen and methanol fuel cells

The transport properties and the swelling behaviour of NAFION and different sulfonated polyetherketones are explained in terms of distinct differences on the microstructures and in the pK_a of the acidic functional groups. The less pronounced hydrophobic/hydrophilic separation of sulfonated polyetherketones compared to NAFION corresponds to narrower, less connected hydrophilic channels and to larger separations between less acidic sulfonic acid functional groups. At high water contents, this is shown to significantly reduce electroosmotic drag and water permeation whilst maintaining high proton conductivity. Blending of sulfonated polyetherketones with other polyaryls even further reduces the solvent permeation (a factor of 20 compared to NAFION), increases the membrane flexibility in the dry state and leads to an improved swelling behaviour. Therefore, polymers based on sulfonated polyetherketones are not only interesting low-cost alternative membrane material for hydrogen fuel cell applications, they may also help to reduce the problems associated with high water drag and high methanol cross-over in direct liquid methanol fuel cells (DMFC). The relatively high conductivities observed for oligomers containing imidazole as functional groups may be exploited in fully polymeric proton conducting systems with no volatile proton solvent operating at temperatures significantly beyond 100°C, where methanol vapour may be used as a fuel in DMFCs.     

Anhydrous proton conducting membranes based on electron-deficient nanoparticles/PBI-OO/PFSA composites for high-temperature PEMFC

PEMFC operating at high temperature (100–200 °C) are expected to have significant advantages but face big challenges in the development of suitable proton exchange membranes. This communication describes novel PBI-OO/PFSA blend membranes, which facilitate proton conduction under anhydrous conditions based on a “proton donor–proton acceptor” concept. The proton conductivity of the blends under anhydrous conditions exceeded that of PFSA by a factor of 50 at ambient temperature and of 2–4 at elevated temperature. Intermolecular interaction between two polymer components was investigated by FT-IR spectroscopy. After incorporation of inorganic electron-deficient compounds (BN nanoparticles), the anhydrous proton conductivity of the composites was higher than that of the bare PFSA by three orders of magnitude at ambient temperature and more than one order of magnitude at 140 °C.     

Characteristics of proton conducting polymer electrolyte based on chitosan acetate complexed with CH3COONH4

The polymer electrolytes based on chitosan and ammonium acetate (CH₃COONH₄) were prepared by solution casting technique and the properties were studied. With the addition of CH₃COONH₄, the amorphous nature of the polymer electrolytes was promoted. The glass transition temperature, activation energy, and conductivity are closely related. Lower the glass transition temperature, lower the activation energy, higher the conductivity. The 40 wt % ammonium acetate doped polymer electrolyte has the lowest glass transition temperature of 369 K, the lowest activation energy of 0.19 eV, and the highest ionic conductivity of 2.87 × 10^?4 S cm^?1 at room temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 549–554, 2009     

Conductivity and thermal behavior of proton conducting polymer electrolyte based on poly (N-vinyl pyrrolidone)

The polymer electrolytes based on poly N-vinyl pyrrolidone (PVP) and ammonium thiocyanate (NH₄SCN) with different compositions have been prepared by solution casting technique. The amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The shift in T_g values and the melting temperatures of the PVP-NH₄SCN electrolytes shown by DSC thermo-grams indicate an interaction between the polymer and the salt. The dependence of T_g and conductivity upon salt concentration have been discussed. The conductivity analysis shows that the 20 mol% ammonium thiocyanate doped polymer electrolyte exhibit high ionic conductivity and it has been found to be 1.7 × 10⁻⁴ S cm⁻¹, at room temperature. The conductivity values follow the Arrhenius equation and the activation energy for 20 mol% ammonium thiocyanate doped polymer electrolyte has been found to be 0.52 eV.     

Fluorinated polyoxadiazole for high-temperature polymer electrolyte membrane fuel cells

For the first time a fluorinated polyoxadiazole doped with phosphoric acid as a proton-conducting membrane for operation at temperatures above 100 °C and low humidities for fuel cells has been reported. Fluorinated polyoxadiazole with remarkable chemical stability was synthesized. No changes in the molecular weight (about 200,000 g mol⁻¹) can be observed when the polymer is exposed for 19 days to mixtures of sulfuric acid and oleum. Protonated membranes with low doping level (0.34 mol of phosphoric acid per polyoxadiazole unit, 11.6 wt.% H₃PO₄) had proton conductivity at 120 °C and RH = 100% in the order of magnitude of 10⁻² S cm⁻¹. When experiments are conducted at lower external humidity, proton conductivity values drop an order of magnitude. However still a high value of proton conductivity (6 × 10⁻³ S cm⁻¹) was obtained at 150 °C and with relative humidity of 1%. In an effort to increase polymer doping, nanocomposite with sulfonated silica containing oligomeric fluorinated-based oxadiazole segments has also been prepared. With the addition of functionalized silica not only doping level but also water uptake increased. For the nanocomposite membranes prepared with the functionalized silica higher proton conductivity in all range of temperature up to 120 °C and RH = 100% (in the order of magnitude of 10⁻³ S cm⁻¹) was observed when compared to the plain membrane (in the order of magnitude of 10⁻⁵ S cm⁻¹).     

锂离子电池电解液的研究进展

综述现今锂离子电池电解液的研究进展 .评估了电解液中锂盐、溶剂、填加剂以及杂质等对电解液的电导、固体电解质相界面 (SEI)的形成、电池循环寿命等的影响     

Parameters influencing transport across conducting electroactive polymer membranes

The parameters which influence electrochemically facilitated transport of electroinactive ions across conducting electroactive polymer membranes have been investigated. The design of membranes and the materials used as well as transport cells and systems have been addressed to improve selectivity and flux. Polypyrrole-para-toluenesulfonate (PPy-pTS) was compared with the copolymer of pyrrole with 3-carboxy-4-methylpyrrole (PPy/PCMP-pTS) and their different chemistries resulted in different membrane selectivities for ions. Platinum mesh was found to be the most suitable auxiliary electrode material and its placement in the cell chamber(s) facilitated ion incorporation/expulsion at the membrane working electrode. This enhanced the flux of ion transport. The flux can also further enhanced by narrowing the distance between the membrane working electrode and the platinum mesh auxiliary electrode(s), and/or by stirring to improve the hydrodynamics. An alternative cell design, namely a dual membrane flow through cell, also proved to be more efficient for ion transport. Good connection geometry to the membrane as well as the application of a square wave pulsed potential waveform to the membrane was found to be essential for achieving high and sustainable flux in ion transport.     

Protonic conducting organic/inorganic nanocomposites for polymer electrolyte membrane

Protonic conducting membrane can be used in many energy technological applications such as fuel cells, water electrolysis, hydrogen separation, sensors and other electrochemical devices. However, polymer electrolyte membrane usually lack thermal stability, resulting in narrow operational temperature windows. So, a new class of polymer membrane with high temperature stability and protonic conductivity is desired for many industrial applications. In this paper, new synthetic routes have been investigated for organic/inorganic nanocomposites hybrid polymer membranes of SiO₂/polymer (polyethylene oxides (PEO); polypropylene oxide (PPO); polytetramethylene oxide (PTMO)). Novel protonic conducting properties have also been investigated. The materials have been synthesized through sol–gel processes in flexible, ductile free-standing thin membrane form. The hybrid membrane has been found to be thermally stable up to 250°C and possess protonic conductivities of approximately 10⁻⁴ S/cm at temperature windows from room temperature to 160°C and relative humidity.     

Nanocomposite blend gel polymer electrolyte for proton battery application

A proton-conducting nanocomposite gel polymer electrolyte (GPE) system, [35{(25 poly(methylmethacrylate) (PMMA) + 75 poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP))?+?xSiO₂}?+?65{1 M NH₄SCN in ethylene carbonate (EC) + propylene carbonate (PC)}], where x?=?0, 1, 2, 4, 6, 8, 10, and 12, has been reported. The free standing films of the gel electrolyte are obtained by solution cast technique. Films exhibit an amorphous and porous structure as observed from X-ray diffractometry (XRD) and scanning electron microscopy (SEM) studies. Fourier transform infrared spectrophotometry (FTIR) studies indicate ion–filler–polymer interactions in the nanocomposite blend GPE. The room temperature ionic conductivity of the gel electrolyte has been measured with different silica concentrations. The maximum ionic conductivity at room temperature has been observed as 4.3?×?10^?3?S?cm^?1 with 2 wt.% of SiO₂ dispersion. The temperature dependence of ionic conductivity shows a typical Vogel-Tamman-Fulcher (VTF) behavior. The electrochemical potential window of the nanocomposite GPE film has been observed between ?1.6 V and 1.6 V. The optimized composition of the gel electrolyte has been used to fabricate a proton battery with Zn/ZnSO₄·7H₂O anode and PbO₂/V₂O₅ cathode. The open circuit voltage (OCV) of the battery has been obtained as 1.55 V. The highest energy density of the cell has been obtained as 6.11 Wh?kg^?1 for low current drain. The battery shows rechargeability up to 3 cycles and thereafter, its discharge capacity fades away substantially.     

燃料电池聚合物电解质膜的研究进展

本文根据聚合物电解质膜燃料电池操作温度、使用的电解质和燃料的不同,将其分为高温质子交换膜燃料电池、低温质子换膜燃料电池、直接甲醇燃料电池和阴离子交换膜燃料电池,综述了它们所用电解质膜的最新进展.第一部分简要介绍了这4种燃料电池的优点和不足.第二部分首先介绍了Nafion膜的结构模型,并对平行柱状纳米水通道模型在介观尺度上进行了修正;接着分别对应用于不同燃料电池的改性膜的改性思路作了分析;最后讨论了用于不同燃料电池的新型质子交换膜的研究,同时列举了性能突出的改性膜和新型质子交换膜.第三部分介绍了阴离子交换膜的研究现状.第四部分对未来聚合物电解质膜的研究作了展望.     

Ordered structures in proton conducting membranes from supramolecular liquid crystal polymers

Highly sulfonated forms of poly(p-phenylene terephthalamide) (PPTA) have been prepared in three different molecular configurations; sulfonated diamine form (S-PPTA), sulfonated terephthalic acid form (S-invert-PPTA), and the bi-sulfonated form (S2-PPTA). All three polymers are water soluble to a certain degree and films were cast from solution for S-PPTA and S-invert-PPTA. S-PPTA films absorb less water than S-invert-PPTA (under controlled humidity conditions) and consequently, the conductivity for this polymer is also slightly lower. Although the conductivities are comparable to Nafion (of the order of 10(-2) to 10(-1) Scm(-1)), proton mobility is more restricted. X-ray diffraction showed that the rigid molecules are aligned in opposite directions for the two polymer films, being homeotropic in S-PPTA films and planar for S-invert-PPTA. SEM analysis demonstrated layering in the same direction as the alignment of the polymer chains. The variation in the polymer alignment is most likely the result of the differences in the solution properties and the film forming process. It is possible, however, that this alignment could be exploited to enhance proton transport and thus these films are of interest for fuel cell membranes.     

Recent developments in polymer characterisation by dynamic mechanical analysis

Examples are given to illustrate the improvements in the Du Pont dynamic mechanical analyser used in conjunction with the Du Pont 1090 thermal analysis system. New techniques and capabilities are discussed and details of the new features are given.     

Recent developments on ion-exchange membranes and electro-membrane processes

Rapid growth of chemical and biotechnology in diversified areas fuels the demand for the need of reliable green technologies for the down stream processes, which include separation, purification and isolation of the molecules. Ion-exchange membrane technologies are non-hazardous in nature and being widely used not only for separation and purification but their application also extended towards energy conversion devices, storage batteries and sensors etc. Now there is a quite demand for the ion-exchange membrane with better selectivities, less electrical resistance, high chemical, mechanical and thermal stability as well as good durability. A lot of work has been done for the development of these types of ion-exchange membranes during the past twenty-five years. Herein we have reviewed the preparation of various types of ion-exchange membranes, their characterization and applications for different electro-membrane processes. Primary attention has been given to the chemical route used for the membrane preparation. Several general reactions used for the preparation of ion-exchange membranes were described. Methodologies used for the characterization of these membranes and their applications were also reviewed for the benefit of readers, so that they can get all information about the ion-exchange membranes at one platform. Although there are large number of reports available regarding preparations and applications of ion-exchange membranes more emphasis were predicted for the usefulness of these membranes or processes for solving certain type of industrial or social problems. More efforts are needed to bring many products or processes to pilot scale and extent their applications.     

Anhydrous proton conducting membranes based on crosslinked graft copolymer electrolytes

A comb-like copolymer consisting of a poly(vinylidene fluoride-co-chlorotrifluoroethylene) backbone and poly(hydroxy ethyl acrylate) side chains, i.e. P(VDF-co-CTFE)-g-PHEA, was synthesized through atom transfer radical polymerization (ATRP) using CTFE units as a macroinitiator. Successful synthesis and a microphase-separated structure of the copolymer were confirmed by proton nuclear magnetic resonance (¹H NMR), FT-IR spectroscopy, and transmission electron microscopy (TEM). This comb-like polymer was crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via the esterification of the –OH groups of PHEA and the –COOH groups of IDA. Upon doping with phosphoric acid (H₃PO₄) to form imidazole–H₃PO₄ complexes, the proton conductivity of the membranes continuously increased with increasing H₃PO₄ content. A maximum proton conductivity of 0.015 S/cm was achieved at 120 °C under anhydrous conditions. In addition, these P(VDF-co-CTFE)-g-PHEA/IDA/H₃PO₄ membranes exhibited good mechanical properties (765 MPa of Young's modulus), and high thermal stability up to 250 °C, as determined by a universal testing machine (UTM) and thermal gravimetric analysis (TGA), respectively.