Proton exchange membranes based on the short-side-chain perfluorinated ionomer

Due to the renovated availability of the base monomer for the synthesis of the short-side-chain (SSC) perfluorinated ionomer, fuel cell membrane development is being pursued using this well known ionomer structure, which was originally developed by Dow in the 1980s. The new membranes under development have the trade name Hyflon Ion. After briefly reviewing the literature on the Dow ionomer, new characterization data are reported on extruded Hyflon Ion membranes. The data are compared to those available in the literature on the Dow SSC ionomer and membranes. Comparison is made also with data obtained in this work or available in the literature on the long-side-chain (LSC) perfluorinated ionomer (Nafion). Thermal, visco-elastic, water absorption and mechanical properties of Hyflon Ion are studied. While the general behavior is similar to that shown in the past by the Dow membranes, slight differences are evident in the hydration behavior at equivalent weight (EW) < 900, probably due to different EW distributions. Measurements on dry membranes confirm that Hyflon Ion has a higher glass transition temperature compared to Nafion, which makes it a more promising material for high temperature proton exchange membrane (PEM) fuel cell operation (T > 100 °C). Beginning of life fuel cell performance has also been confirmed to be higher than that given by a Nafion membrane of equal thickness.     

Proton exchange membranes based on hydrophilic-hydrophobic multiblock copolymers using different hydrophobic oligomer

Although sulfonated aromatic polymers are thought to be one of the promising materials for proton exchange membranes, most of them suffer from significant drop of proton conductivity with decrease in humidity, which causes poor cell performance under partially hydrated condition. In this study, to improve proton conduction at low hydration level, two different multiblock copolymer membranes based on different hydrophobic oligomers are prepared and their hydrophilic/hydrophobic phase-separated morphology is examined. Both multiblock copolymer membranes show better developed phase separation than the random copolymer membrane. Multiblock copolymer having more hydrophobic oligomer exhibits better interconnection between hydrophilic channels than that having less hydrophobic oligomer. This can lead to an improvement of both proton conductivity and cell performance under partially hydrated condition.     

Proton exchange membranes based on semi-interpenetrating polymer networks of fluorine-containing polyimide and Nafion

A series of reinforced composite membranes as proton exchange membranes were prepared from Nafion^®212 and crosslinkable fluorine-containing polyimides (FPI). FPI was prepared from the polymerization of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFMB), and 3,5-diaminobenzoic acid (DABA). Then FPI was thermally crosslinked during the membrane preparation and formed the semi-interpenetrating polymer networks (semi-IPN) structure in the composite membranes. The thermal properties of the composite membranes were characterized by thermogravimetric analysis. The crosslinking density of FPI in the composite membranes was evaluated by the gel fraction. These membranes showed excellent thermal stabilities and good oxidative stabilities. Compared with Nafion^®212, the obtained composite membranes displayed much improved mechanical properties and dimensional stabilities. The tensile strength of the composite membranes was more than twice that of Nafion^®212. The composite membranes exhibited high proton conductivity, which ranged from 2.3 × 10⁻² S cm⁻¹ to 9.1 × 10⁻² S cm⁻¹. All membranes showed an increase in proton conductivity with temperature elevation.     

Proton conductive membranes based on doped sulfonated polytriazole

This work reports the preparation and characterization of proton conducting sulfonated polytriazole membranes doped with three different agents: 1H-benzimidazole-2-sulfonic acid, benzimidazole and phosphoric acid. The modified membranes were characterized by scanning electron microscopy (SEM), infrared spectra, thermogravimetric analysis (TGA), dynamical mechanical thermal analysis (DMTA) and electrochemical impedance spectroscopy (EIS). The addition of doping agents resulted in a decrease of the glass transition temperature. For membranes doped with 85 wt.% phosphoric acid solution proton conductivity increased up to 2·10⁻³ S cm⁻¹ at 120 °C and at 5% relative humidity. The performance of the phosphoric acid doped membranes was evaluated in a fuel cell set-up at 120 °C and 2.5% relative humidity.     

High temperature proton exchange porous membranes based on polybenzimidazole/ lignosulfonate blends: Preparation,morphology and physical and proton conductivity properties

Porous polybenzimidazole (PBI) based blend membranes were prepared by adding different amounts of lignosulfonate (LS) in the presence of LiCl salt. The morphology characteristics of the PBI/LS blends were investigated by FT-IR, atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses. The relation between the membrane morphology and membrane proton conductivity was studied. Results showed that LS content has a significant influence on the membrane morphology. High amount of LS in the blend created micro-pores within the membrane where increase in the LS content up to 20 wt% resulted in membranes containing pores with a mean diameter of about 0.8 μm. The resulting PBI/LS (0–20 wt%) membranes indicated high PA doping levels, ranging from 3 to 16 mol of PA per mole of PBI repeat units, which contributed to their unprecedented high proton conductivities of 4–96 mS cm⁻¹, respectively, at 25 °C. The effect of temperature on the proton conductivity of blends was also investigated. The results showed that by rising the temperature, the proton conductivity increases in PBI/LS blends. In the blend containing 20 wt% LS, proton conductivity increased from 98 mS cm⁻¹ at 25 °C to 187 mS.cm⁻¹at 160 °C which can be considered as an excellent candidate for use in both high and low temperature proton exchange membrane fuel cells.     

Proton exchange membranes based on semi-interpenetrating polymer networks of Nafion and poly(vinylidene fluoride) via radiation crosslinking

A new method to prepare proton exchange membranes based on semi-interpenetrating polymer networks (semi-IPN) of Nafion^® and poly(vinylidene fluoride) (PVDF) via radiation crosslinking was proposed. The tensile strength, degree of crosslinking, water uptake, and swelling ratio of the composite membranes were studied. Compared to the recast Nafion^®212 membrane, the composite membranes show much better mechanical properties and improved dimensional stability. The tensile strength of the composite membranes ranges from 34.3 MPa to 53.4 MPa, which is higher than that of the recast Nafion^®212 membrane (23.9 MPa). The dimensional stability of the composite membranes also increases with increasing PVDF content in the membranes. The composite membranes show considerable proton conductivity even at 100-120 °C. The membrane containing 40% PVDF shows the highest proton conductivity of 3.37 × 10⁻² S/cm at 115 °C. These properties make them a great potential in polymer electrolyte membrane fuel cells (PEMFC).     

Proton conducting membranes based on sulfonated PEEK-WC polymer for PEMFCs

Proton conducting membranes have been prepared from chloro-sulfonated polyetheretherketone with cardo group polymers at various sulfonation degree via casting solutions using dimethylformamide as a solvent. The proton conductivity of sulfonated polyetheretherketone with cardo group membranes has been evaluated in the temperature range between 80 and 120 °C and the best result of this work has been achieved at 120 °C and sulfonation degree equal to 60% with a value equal to 6.7·10⁻² S/cm. Furthermore, this sample shows an open circuit voltage varying from 0.881 V at 80 °C to 0.867 V at 120 °C, pointing out that the membrane performance is not greatly affected by a temperature variation. Nevertheless, an increase of temperature from 80 to 120 °C makes possible an increase of the cell resistance varying from 0.17 to 0.24 Ω cm². Thus, the present study investigates the performance of sulfonated polyetheretherketone with cardo group membranes in terms of polarization curves, open circuit voltage, cell resistance and proton conductivity in order to propose them for proton exchange membrane fuel cell applications, particularly at T > 100 °C.     

Synthesis and properties of novel proton exchange membranes based on sulfonated polyethersulfone and N-phthaloyl chitosan blends for DMFC applications

Chitosan is modified by phthaloylation using an excess of phthalic anhydride at 130 °C and blended with the sulfonated polyethersulfone (SPES) to produce composite blend membranes. In particular the introduction of the phthaloyl group into the chitosan matrix increases its solubility in organic solvent, film formability, flexibility, low methanol permeability and with suitable ion conductivity. SPES and N-phthaloyl chitosan (NPHCs) blend membranes with various compositions were prepared and detailed investigation on water uptake, proton conductivity and methanol permeability has been conducted for its suitability in fuel cell environments. Methanol permeability studies envisaged that NPHCs blend membranes are impervious to methanol. The thermograms display the good thermal stabilities of blend membranes than Nafion-117. Relatively high selectivity parameter values of these membranes indicated their greater advantages over Nafion-117 membrane for targeting on fuel cell applications, especially in direct methanol fuel cell (DMFC) environments.     

Proton conducting membranes based on Poly(2,5-benzimidazole) (ABPBI)–Poly(vinylphosphonic acid) blends for fuel cells

Polymer electrolyte membranes (PEM) were fabricated by blending of Poly(2,5-benzimidazole) (ABPBI) and Poly(vinylphosphonic acid) (PVPA) at several stoichiometric ratios with respect to monomer repeating units. The characterization of the membranes were carried out by using Fourier-transform infrared spectroscopy (FT-IR) for inter-polymer interactions, scanning electron microscope (SEM) for surface morphology as well as homogeneity and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) for thermal properties. Water uptake measurements were made to investigate the swelling character the blends that was changed with PVPA composition. The spectroscopic measurements and water uptake studies suggested the complexation between ABPBI and PVPA that inhibited dopant exclusion up on swelling in excess water. Proton conductivities of the hydrated and anhydrous samples were measured using impedance spectroscopy. Although the proton conductivity of the blends was lower in the anhydrous state such as 1.8 × 10⁻⁶ S/cm at 150 °C for ABPBI:PVPA with (1:2), it increased to 0.004 S/cm for ABPBI:PVPA (1:4) at 20 °C (RH = 50%).     

New non-fluoridated hybrid proton exchange membranes based on commercial precursors

New hybrid proton conducting membranes based on sulfonated copolymers of styrene and allyl glycidyl ether using tetraethyl orthosilicate were syntheses. The composition and structure of the copolymers and membranes has been proven by elemental analysis, IR and NMR spectroscopy. Based on quantum chemical calculations a sulfonation mechanism of copolymers was proposed. The characteristics of membranes were evaluated by thermal analysis, dynamic mechanical analysis, electrochemical impedance spectroscopy, water uptake, swelling and ion exchange capacity tests. The hybrid membranes are characterized by high proton conductivity of 4.21 10⁻² S cm⁻¹ (70 °C, 75% RH), activation energy of proton transport (24.5 kJ mol⁻¹), ion-exchange capacity (2.1 mmol g⁻¹), and thermal stability up to 260°С. The hybrid membranes showed water uptake of 6 and 51% at 30 °C and 100 °C, respectively. The suitability of the hybrid membranes toward fuel cell applications was tested through a single cell analysis.     

Proton conducting membranes based on poly(acrylonitrile-co-styrene sulfonic acid) and imidazole

The development of polymer electrolyte membranes based on poly(acrylonitrile-co-styrene sulfonic acid) (PAN-co-PSSA) is reported. PAN-co-PSSA copolymers with two different copolymer compositions were synthesized via free radical polymerization, and confirmed by ¹H NMR and elemental analysis. Homogeneous PAN-co-PSSA membranes were obtained via solvent cast method. PAN-co-PSSA membrane with the ratio of AN to SSA in the copolymer of 16:1 exhibited higher water uptake and IEC than that of 22:1. PAN-co-PSSA (16:1) was then doped with imidazole at molar ratios of 1:0.5, 1:1, and 1:2. Membrane functionalities were studied using FTIR. Thermal and mechanical properties were investigated using thermogravimetric analysis and dynamic mechanical analysis, respectively. All prepared membranes showed thermal stability of up to 180 °C, and showed superior mechanical property to that of Nafion^® 117 within the studied temperature range. In addition, good oxidative stability was observed. Proton conductivity at room temperature was found to depend highly on relative humidity, and was enhanced through doping with imidazole. A maximum proton conductivity of 2.1 × 10^?3 S/cm was achieved from membrane 1:2 saturated with water vapor. At higher temperatures (120–180 °C), proton conductivities of imidazole-doped membranes increased with increasing temperature and imidazole content.     

Proton exchange membrane fuel cell degradation prediction based on Adaptive Neuro-Fuzzy Inference Systems

This paper studies the prediction of the output voltage reduction caused by degradation during nominal operating condition of a PEM fuel cell stack. It proposes a methodology based on Adaptive Neuro-Fuzzy Inference Systems (ANFIS) which use as input the measures of the fuel cell output voltage during operation. The paper presents the architecture of the ANFIS and studies the selection of its parameters. As the output voltage cannot be represented as a periodical signal, the paper proposes to predict its temporal variation which is then used to construct the prediction of the output voltage. The paper also proposes to split this signal in two components: normal operation and external perturbations. The second component cannot be predicted and then it is not used to train the ANFIS. The performance of the prediction is evaluated on the output voltage of two fuel cells during a long term operation (1000 h). Validation results suggest that the proposed technique is well adapted to predict degradation in fuel cell systems.     

Proton exchange membrane fuel cell ageing forecasting algorithm based on Echo State Network

Regarded as a promising technology, proton exchange membrane fuel cell (PEMFC) are not far from a large-scale deployment. However, some improvements are still needed to extend the lifetime of these systems. The discipline of PHM (Prognostic and health management) seems like a great solution to help against this problem. The objective is to predict the evolution of the behavior of a system using algorithms to estimate in advance when a fault occurs. This knowledge of the default before its occurrence allows to anticipate a decision, often by using a fault-tolerant control. Different methodologies exist to make a prognostic algorithm: model based, data based or a hybridization between these two previous methodologies. This paper will focus on the data based prognosis, mainly due to the fact that all of the phenomena involved in the degradation of a PEMFC are not yet fully known, thus not yet modeled. The first innovation of this paper concern the use of a new neural network paradigm, the Echo State Network, which is a part of Reservoir Computing methods. This new paradigm gives very interesting results, with a mean average percentage error less than 5% in our study case. The other contribution is the definition of a filtering method, regarding to the test bench, by evaluating the Hurst exponent of the signal filtered by wavelet.     

Proton exchange membrane fuel cell system diagnosis based on the multivariate statistical method

Although electric-powered vehicles have developed rapidly in recent years, with significant progress in the lithium power battery industry, the Fuel Cell Electric Vehicle (FCEV) is still a competitive choice for a clean transportation solution, because of its extended driving range, zero emissions, and fast fuel recharging capability. In particular the fuel cell hybrid bus used for city traffic is the FCEV type most likely to be commercialized. Demonstration programs for a fuel cell bus fleet have been operated for a few years in China. It is necessary to develop comprehensive diagnostic tools to increase the reliability of these systems, because fuel cell city buses serve large numbers of passengers using public transportation. This paper presents a diagnostic analysis and implementation study based on the Principal Component Analysis (PCA) method for the fuel cell system. This diagnostic system was successfully implemented for detecting a fuel cell stack sensor network failure in the fuel cell bus fleet at the Shanghai Expo in 2010.     

Proton exchange membranes containing densely alkyl sulfide sulfonated side chains for vanadium redox flow battery

Due to further increase the performance of aromatic sulfonated proton exchange membrane (PEM) and make it play a better role in vanadium redox flow battery (VRFB), a series of poly(aryl ether sulfone)s containing eight alkyl sulfide sulfonated side chains (8SPAES-xx) are designed and synthesized. Their molecular structure, phase morphology and some selective properties were investigated in detail, respectively. It is confirmed that 8SPAES-xx membranes have clear hydrophilic/hydrophobic phase separation morphology. These membranes with the ion exchange capacity values of 1.08–1.61 mmol/g exhibit excellent ionic conductivity as well as moderate water uptake and good dimensional stability, and their values are in the range of 25–96 mS/cm, 8–28% and 5–17% at 30 °C, respectively. Among them, the proton conductivity of 8SPAES-12 membrane is 82 mS/cm at 30 °C, which exceeds the ionic conductivity of Nafion 117 (79 mS/cm). The membrane also shows high ion selectivity and excellent battery performance. At current density of 60 mA/cm², the highest energy efficiency of VRFB with 8SPAES-12 membrane is 87.3%, which is higher than that of Nafion 117 (83.8%). Furthermore, the efficiency of VRFB with 8SPAES-12 membrane remains good cycle stability.     

Proton exchange membrane fuel cell system diagnosis based on the signed directed graph method

The fuel-cell powered bus is becoming the favored choice for electric vehicles because of its extended driving range, zero emissions, and high energy conversion efficiency when compared with battery-operated electric vehicles. In China, a demonstration program for the fuel cell bus fleet operated at the Beijing Olympics in 2008 and the Shanghai Expo in 2010. It is necessary to develop comprehensive proton exchange membrane fuel cell (PEMFC) diagnostic tools to increase the reliability of these systems. It is especially critical for fuel-cell city buses serving large numbers of passengers using public transportation. This paper presents a diagnostic analysis and implementation study based on the signed directed graph (SDG) method for the fuel-cell system. This diagnostic system was successfully implemented in the fuel-cell bus fleet at the Shanghai Expo in 2010.     

PVDF–PEO blends based microporous polymer electrolyte: Effect of PEO on pore configurations and ionic conductivity

A novel microporous polymer electrolyte based on poly(vinylidene fluoride) and poly(ethylene oxide) (PVDF–PEO) blends was prepared by a simple phase inversion technique, in which the addition of PEO can obviously improve the pore configuration, such as pore size, porosity, and pore connectivity of PVDF-based microporous membranes, and hence, the room temperature ionic conductivity was greatly enhanced. The highest porosity of about 84% and ionic conductivity of about 2 mS cm⁻¹ can be obtained when the weight ratio of PEO to PVDF is 50%. This implies that PVDF–PEO blends based microporous polymer electrolyte can be used as candidate electrolyte and/or separator material for high-performance rechargeable lithium batteries.     

Hydrocarbon and partially fluorinated sulfonated copolymer blends as functional membranes for proton exchange membrane fuel cells

Polymer blending is recognized as a valuable technique used to modify and improve the mechanical, thermal, and surface properties of two different polymers or copolymers. This paper investigated the solution properties and membrane properties of a biphenol-based disulfonated poly (arylene ether sulfone) random copolymer (BPS-35) with hexafluoroisopropylidene bisphenol based sulfonated poly (arylene ether sulfone) copolymers (6FSH) and an unsulfonated biphenol-based poly (arylene ether sulfone)s. The development of blended membranes with desirable surface characteristics, reduced water swelling and similar proton conductivity is presented.     

石蜡/SEBS复合相变材料热疗鼻贴的研究

以热塑性弹性体(SEBS)为基体,以四种不同石蜡(OP44E、Paraffin46-48、OP50E、OP55E)作为相变材料,通过物理吸附和平板硫化法制备得到了具有不同相变温度的石蜡/SEBS复合相变材料热疗鼻贴.测量了复合相变材料的硬度、相变温度和相变潜热以及热疗鼻贴的控温效果.结果表明:四种石蜡/SEBS复合相变...     

Novel high-performance nanocomposite proton exchange membranes based on poly (ether sulfone)

In the present research, proton exchange membranes based on partially sulfonated poly (ether sulfone) (S-PES) with various degrees of sulfonation were synthesized. It was found that the increasing of sulfonation degree up to 40% results in the enhancement of water uptake, ion exchange capacity and proton conductivity properties of the prepared membranes to 28.1%, 1.59 meq g⁻¹, and 0.145 S cm⁻¹, respectively. Afterwards, nanocomposite membranes based on S-PES (at the predetermined optimum sulfonation degree) containing various loading weights of organically treated montmorillonite (OMMT) were prepared via the solution intercalation technique. X-ray diffraction patterns revealed the exfoliated structure of OMMT in the macromolecular matrices. The S-PES nanocomposite membrane with 3.0 wt% of OMMT content showed the maximum selectivity parameter of about 520,000 S s cm⁻³ which is related to the high conductivity of 0.051 S cm⁻¹ and low methanol permeability of 9.8 × 10⁻⁸ cm² s⁻¹. Furthermore, single cell DMFC fuel cell performance test with 4 molar methanol concentration showed a high power density (131 mW cm⁻²) of the nanocomposite membrane at the optimum composition (40% of sulfonation and 3.0 wt% of OMMT loading) compared to the Nafion^®117 membrane (114 mW cm⁻²). Manufactured nanocomposite membranes thanks to their high selectivity, ease of preparation and low cost could be suggested as the ideal candidate for the direct methanol fuel cell applications.