共查询到20条相似文献,搜索用时 15 毫秒
1.
Fabrication and characterization of PFSI/ePTFE composite proton exchange membranes of polymer electrolyte fuel cells 总被引:1,自引:0,他引:1
PFSI/ePTFE composite proton exchange membranes were fabricated by impregnating perfluorosulfonic acid resin (PFSI resin, Nafion) into chemically modified expanded PTFE (ePTFE) matrix. Chemical modification of sodium-naphthalene treatment and N-methylol acrylamide (NMA) grafting decreased the contact angle of the as-received ePTFE from 125 ± 0.5° to 67 ± 0.5°, effectively converting the as-received hydrophobic ePTFE to a hydrophilic ePTFE matrix. The composite membrane fabricated with the hydrophilic ePTFE have higher impregnated PFSI loading, much lower porosity and better PTFE/PFSI interface contact, as compared to the composite membranes with the as-received ePTFE. This leads to much lower gas permeability and significantly improves the durability under an accelerated dry/wet cycle test. The fuel cell made from the PFSI/ePTFE composite membranes with hydrophilic ePTFE showed superior performance as compared to that with the composite membrane made from the as-received ePTFE and Nafion 211 membrane. 相似文献
2.
In the present work, novel gel-based composite polymer electrolytes for lithium batteries were prepared by introducing a hierarchical mesoporous silica network to the poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)-based gel electrolytes. As compared with the PVDF-HFP-based gel electrolytes with/without conventional nano-sized silica fillers, the novel electrolytes have shown more homogeneous microstructure, higher ionic conductivity and better mechanical stability, which could be caused by the strong silica network and the effective interactions among the polymer, the liquid electrolytes and the silica. Moreover, the cell with this kind of electrolytes could achieve a discharge capacity as much as 150 mAh g−1 at room temperature (LiCoO2 as the cathode active material), with high Coulomb efficiency. 相似文献
3.
Chemical anchoring of silica nanoparticles onto polyaniline (PANI) chains was conducted through electro-co-polymerization of aniline and N-substituted aniline grafted on surfaces of silica nanoparticles. The grafting of N-substituted aniline on surfaces of silica nanoparticles were realized through hydrolysis of triethoxysilylmethyl N-substituted aniline (ND42) and the following condensation reaction with silanol groups on surfaces of SiO2. Organic-inorganic interactions between PANI and SiO2 involved in electro-co-polymerization process pushed the polymer chains apart and so facilitated the 1D growth of the polymer. Hence, the obtained hybrid film PANI/ND42-SiO2 displayed nano-fibrous morphologies (ca. 50 nm in diameter). Consequently, PANI/ND42-SiO2 exhibited an average specific capacitance of 380 F g−1, ca. 40% higher than that of PANI/SiO2 (276 F g−1). The hybrid film also showed improved cyclic stability. 相似文献
4.
Hongting Pu Yujie Qin Liming Tang Xinrong Teng Zhihong Chang 《Electrochimica acta》2009,54(9):2603-9923
Anhydrous proton conducting membranes based on sulfonated polyimide (sPI) and imidazole derivatives were prepared. The acid-base composite membranes show a good chemical oxidation stability and high thermal stability. The addition of imidazole derivatives in sPIs can improve the chemical oxidation stability of the composite membranes enormously, and even much better than that of pure sPI. The proton conductivity of a typical sPI/xUI(2-undecylimidazole) composite membrane can reach 10−3 S cm−1 at 180 °C under the anhydrous condition. The proton conductivity of the acid-base composite membranes increases significantly with increasing content of UI. Moreover, UI in sPI/xUI composite membrane is difficult to be brought out by the vapor due to the existence of long hydrophobic moiety, which will improve the stability and lifetime of the membranes in the fuel cells. 相似文献
5.
Poly(tetrafluoroethylene) PTFE/PBI composite membranes doped with H3PO4 were fabricated to improve the performance of high temperature polymer electrolyte membrane fuel cells (HT-PEMFC). The composite membranes were fabricated by immobilising polybenzimidazole (PBI) solution into a hydrophobic porous PTFE membrane. The mechanical strength of the membrane was good exhibiting a maximum load of 35.19 MPa. After doping with the phosphoric acid, the composite membrane had a larger proton conductivity than that of PBI doped with phosphoric acid. The PTFE/PBI membrane conductivity was greater than 0.3 S cm−1 at a relative humidity 8.4% and temperature of 180 °C with a 300% H3PO4 doping level. Use of the membrane in a fuel cell with oxygen, at 1 bar overpressure gave a peak power density of 1.2 W cm−2 at cell voltages >0.4 V and current densities of 3.0 A cm−2. The PTFE/PBI/H3PO4 composite membrane did not exhibit significant degradation after 50 h of intermittent operation at 150 °C. These results indicate that the composite membrane is a promising material for vehicles driven by high temperature PEMFCs. 相似文献
6.
Poly(vinyl alcohol) membrane was coated with organic-silica nanocomposite derived from perhydropolysilazane. For organic composite part, polystyrene-block-poly(4-vinyl phenol) [SP], poly(tert-butyl acrylate-co-2-hydroxyethyl methacrylate) [BA] and poly(butyl methacrylate-co-2-hydroxyethyl methacrylate) [BMA] were used. Water vapor barrier property of coat membrane was measured at relative humidity = 96% by a cup method. The coat films of nanocomposites with SP-silica and BA-silica showed better water vapor barrier property than those of the silica coat film without organic polymer and BMA-silica composites. The surface morphologies of the coat films were investigated by scanning electron microscopy and atomic force microscopy. The addition of organic polymer to silica prevented the crack formation of coat layer on the substrate. 相似文献
7.
Masanori Yamada 《Polymer》2005,46(9):2986-2992
The development of anhydrous proton conducting membrane is important for the operation of polymer electrolyte membrane fuel cell (PEMFC) at intermediate temperature (100-200 °C). In this study, we have investigated the acid-base hybrid materials by mixing of strong phosphonic acid polymer of poly(vinylphosphonic acid) (PVPA) with the high proton-exchange capacity and organic base of heterocycle, such as imidazole (Im), pyrazole (Py), or 1-methylimidazole (MeIm). As a result, PVPA-heterocycle composite material showed the high proton conductivity of approximately 10−3 S cm−1 at 150 °C under anhydrous condition. In particular, PVPA-89 mol% Im composite material showed the highest proton conductivity of 7×10−3 S cm−1 at 150 °C under anhydrous condition. Additionally, the fuel cell test of PVPA-89 mol% Im composite material using a dry H2/O2 showed the power density of approximately 10 mW cm−2 at 80 °C under anhydrous conditions. These acid-base anhydrous proton conducting materials without the existence of water molecules might be possibly used for a polymer electrolyte membrane at intermediate temperature operations under anhydrous or extremely low humidity conditions. 相似文献
8.
Chang-shen Ye Hong-xing Wang Guo-qiang Huang Ting Qiu 《Chemical Engineering Research and Design》2013
To reduce the high energy consumption during the traditional ordinary distillation process for recycling N,N-dimethyl formamide (DMF), this paper utilized the NKA-II macroporous adsorptive resin in combination with a distillation process to recycle DMF in wastewater. First, the adsorption equilibrium data were measured in the intermittent agitation tank, which showed that the DMF adsorption equilibrium on the NKA-II resin complies with the Henry equation. The dynamic experimental studies indicated that the adsorption temperature has little effect on the adsorption process; the flow rate and the bed height affect the breakthrough time but have little effect on the mass transfer zone. With the combination of the fixed-bed adsorption model and the breakthrough curve, the surface diffusion coefficient of the DMF on the resin in the fixed bed was approximately 3.50 × 10−10 to 1.06 × 10−9 m2 s−1. The simulated values were in good agreement with the breakthrough curves determined by experiments. Furthermore, ethanol was selected as a better desorption agent. The appropriate desorption conditions were determined to be a flow rate of 8.00 × 10−5 m s−1 to 1.58 × 10−4 m s−1 and a temperature of 308–318 K. Under these conditions, the desorption rates were all greater than 99%. Finally, wastewater that contained 5% DMF was used as an example to analyze the energy consumption. The results indicated that the adsorption–distillation process can reduce the energy consumption by 79%. The adsorption–distillation process has a good applicable value for the recovery of DMF in wastewater, especially for wastewater with a low concentration of DMF. 相似文献
9.
Microporous poly(acrylonitrile-methyl methacrylate) membrane as a separator of rechargeable lithium battery 总被引:1,自引:0,他引:1
We studied microporous poly(acrylonitrile-methyl methacrylate), AMMA, membrane as the separator of Li/LiMn2O4 cell. The porous AMMA membrane was prepared by the phase inversion method with N,N-dimethylformamide (DMF) as the solvent and water as the non-solvent. We observed that morphology of the resulting membrane was strongly affected by the concentration of polymer solution: low concentration produced finger-like pores with dense skin on two surfaces of the membrane, while high concentration yielded open voids with dense layer on the other surface of the membrane. Regardless of their morphology, both membranes could be rapidly wetted by the liquid electrolyte (1.0 m LiBF4 dissolved in 1:3 wt.% mixture of ethylene carbonate (EC) and γ-butyrolactone (GBL)), and could be swollen at elevated temperatures, which resulted in the formation of a microporous gel electrolyte (MGE). It was shown that the resulting MGE not only had high ionic conductivity and but also had good compatibility with metal lithium even at 60 °C. Cyclic voltammetric test showed that the MGE had an electrochemical window of 4.9 V versus Li+/Li. At room temperature, the Li/MGE/LiMn2O4 cell showed excellent cycliability with a specific capacity of 121-125 mA h g−1 LiMn2O4. It was shown that even at 60 °C good mechanical strength of the MGE remained. Therefore, the MGE is suitable for the application of battery separator at elevated temperatures. 相似文献
10.
A new strategy to prepare the reinforced composite membranes for polymer electrolyte membrane fuel cells (PEMFCs), which can work both in humidified and anhydrous state, was proposed via constructing semi-interpenetrating polymer network (semi-IPN) structure from polybenzimidazole (PBI) and Nafion®212, with N-vinylimidazole as the crosslinker. The crosslinkable PBI was synthesized from poly(2,2′-(m-phenylene)-5,5′-bibenzimidazole) and p-vinylbenzyl chloride. The semi-IPN structure was formed during the membrane preparation. The composite membranes exhibit excellent thermal stability, high-dimensional stability, and significantly improved mechanical properties compared with Nafion®212. The proton transport in the hydrated composite membranes is mainly contributed by the vehicle mechanism, with proton conductivity from ∼10−2 S/cm to ∼10−1 S/cm. When the temperature exceeds 100 °C, the proton conductivity of the semi-IPN membranes decreases quickly due to the dehydration of the membranes. Under anhydrous condition, the proton conductivity of the membranes will drop to ∼10−4 S/cm, which is also useful for intermediate temperature (100-200 °C) PEMFCs. The benzimidazole structure of PBI and the acidic component of Nafion® provide the possibility for the proton mobility via structure diffusion involving proton transfer between the heterocycles with a corresponding reorganization of the hydrogen bonded network. 相似文献
11.
Proton-conducting polymer electrolytes based on methacrylates were prepared by direct, radical polymerization of ethyl (EMA), 2-ethoxyethyl (EOEMA), and 2-hydroxyethyl methacrylate (HEMA). Samples with embedded solutions of phosphoric acid in propylene carbonate (PC), γ-butyrolactone (GBL), N,N-dimethylformamide (DMF) and their mixtures were studied using impedance, voltammetrical and thermogravimetric methods. Membranes of long-term stability exhibit ionic conductivity up to 6.7 × 10−5 S cm−1 at 25 °C reached for the sample PEMA-PC-H3PO4 (31:42:27 mol.%). The accessible electrochemical potential window is 2.2-3 V depending on the working electrode material (glassy carbon or platinum). The thermogravimetric analysis shows that the membranes are thermally stable up to 110-130 °C. 相似文献
12.
Nafion/Analcime and Nafion/Faujasite composite membranes for polymer electrolyte membrane fuel cells
The Nafion/zeolite composite membranes were synthesized for polymer electrolyte fuel cells (PEMFCs) by adding zeolite in the matrix of Nafion polymer. Two kinds of zeolites, Analcime and Faujasite, having different Si/Al ratio were used. The physico-chemical properties of the composite membranes such as water uptake, ion-exchange capacity, hydrogen permeability, and proton conductivity were determined. The fabricated composite membranes showed the significant improvement of all tested properties compared to that of pure Nafion membrane. The maximum proton conductivity of 0.4373 S cm−1 was obtained from Nafion/Analcime (15%) at 80 °C which was 6.8 times of pure Nafion (0.0642 S cm−1 at 80 °C). Conclusively, Analcime exhibited higher improvement than Faujasite. 相似文献
13.
A simple and easy sol-gel approach has been developed to directly synthesize in situ three-dimensionally interconnected uniform ordered bimodal porous silica (BPS) incorporating both the macroporosity and mesoporosity in the lattice without extra synthesis process performed in previous work. Multimodal porous carbon (MPC) was fabricated through the inverse replication of the BPS. The unique structural characteristics such as well-developed 3-D interconnected ordered macropore framework with open mesopores embedded in the macropore walls, large surface area (1120 m2 g−1) and mesopore volume (1.95 cm3 g−1) make MPC very attractive as an anode catalyst support in polymer exchange membrane fuel cell. The MPC-supported Pt-Ru alloy catalyst has demonstrated much higher power density toward hydrogen oxidation than the commercial carbon black Vulcan XC-72-supported ones. 相似文献
14.
Silicon-containing sulfonated polystyrene/acrylate-poly(vinyl alcohol) (Si-sPS/A-PVA) and Si-sPS/A-PVA-phosphotungstic acid (Si-sPS/A-PVA-PWA) composite membranes were fabricated by solution blending and physical and chemical crosslinking methods to improve the properties of silicon-containing sulfonated polystyrene/acrylate (Si-sPS/A) membranes. FTIR spectra clearly show the existence of various interactions and a crosslinked silica network in composite membranes. The potential of the composites to act as proton exchange membranes in direct methanol fuel cells (DMFCs) was assessed by studying their thermal and hydrolytic stability, swelling, methanol diffusion coefficient, proton conductivity and selectivity. TGA measurements show that the composite membranes possess good thermal stability up to 190 °C, satisfying the requirement for fuel cell operation. Compared to the unmodified membrane, the composites exhibit less swelling and a superior methanol barrier. Most importantly, all of the composite membranes have significantly lower methanol diffusion coefficients and significantly higher selectivity than those of Nafion® 117. The Si-sPS/A-20PVA-20PWA membrane is the best applicant for use in DMFCs because it exhibits an optimized selectivity value (5.93 × 105 Ss cm−3) that is approximately 7.8 times of that of the unmodified membrane and is 27.8 times higher than that of Nafion® 117. 相似文献
15.
Miklós Czaun 《Polymer》2008,49(25):5410-5416
A polymerizable l-phenylalanine-derived monomer (N′-octadecyl-Nα[4-(acryloyloxy)-butanoyl]-l-phenylalanineamide (3)) has been newly synthesized and characterized. We reported an advanced approach to molecular shape recognitive hybrid materials that involves immobilization of radical initiator on mesoporous silica particles (average diameter, pore size and surface area are 4 μm, 12 nm, and 300 m2 g−1, respectively) and surface-initiated atom transfer radical polymerization of monomer 3 from initiator-grafted particles. All samples were characterized by elemental analysis, thermogravimetric analysis, diffuse reflectance infrared Fourier transform spectroscopy, solid state NMR measurements (13C CP/MAS NMR and 29Si CP/MAS NMR), differential scanning calorimetry and scanning electron microscopy. The obtained polymer-silica hybrid material was used as a stationary phase for reversed-phase high performance liquid chromatography (RP-HPLC) to investigate its molecular shape recognition ability towards polycyclic aromatic hydrocarbons (PAHs). The new composite material showed better planarity selectivity than octadecylsilane stationary phase as a conventional RP-HPLC packing material and also enhanced linearity selectivity compared with the recently reported poly(N′-octadecyl-Nα-(4-vinyl)-benzoyl-l-phenylalanineamide)-grafted silica. Such selectivity enhancement can be attributed to the combination of hydrophobic effect due to octadecyl chains and multiply carbonyl π-benzene π interaction between the amide groups of the stationary phase and delocalized electrons of PAHs. 相似文献
16.
Joel Ramírez-Salgado 《Electrochimica acta》2007,52(11):3766-3778
Up to now, many research groups work to improve the electrical and mechanical properties of membranes with a low cost of production. The biopolymers could be an answer to produce proton membranes at low cost. This work demonstrates that the intrinsic membrane polymer and clays properties can help to develop a novel proton exchange membranes. Biopolymer composites (chitosan-oxide compounds) present conductivity between 10−3 and 10−2 S cm−1. The measurements were calculated by EIS (1 MHz-0.05 Hz) using the two-electrode configuration. Different oxides were used: MgO, CaO, SiO2, Al2O3. The ionic conductivities were compared with Nafion®'s in the same conditions of P and T. The catalyst layer/membrane ensemble was made during the design with the subsequent demonstration as membrane electrode assemblies and finally the fuel cell was built. Our focus was to increase the compatibility between the proton basic polymer exchange membrane and basic clays as CaO and test a new kind of fuel cell. 相似文献
17.
Flexible bi-continuous mesostructured polymer/inorganic composite membranes have been synthesized by undertaking co-assemblies of surfactants and inorganic sol-gel processes inside pores of a preformed porous polymer membrane such as PP porous membrane Celgard® 2400. The pores are interconnected across the membranes, therefore the continuity of the inorganic mesopores across the membranes is guaranteed in principle. The solvent ethanol used for silica sol is conducive to the synthesis of inorganic materials such as silica within the pores although the PP membrane is hydrophobic. The composite membranes show new properties such as transparency, flexibility, uniform nanosized pores and enhanced permeability. 相似文献
18.
Hydrophilic fumed silica (SiO2)/polyacrylonitrile (PAN) composite electrolyte membranes were prepared by electrospinning composite solutions of SiO2 and PAN in N,N-dimethylformamide (DMF). Among electrospinning solutions with various SiO2 contents, the 12 wt% SiO2 in PAN solution has highest zeta potential (−40.82 mV), and exhibits the best dispersibility of SiO2 particles. The resultant 12 wt% SiO2/PAN nanofiber membrane has the smallest average fiber diameter, highest porosity, and largest specific surface area. In addition, this membrane has a three-dimensional network structure, which is fully interconnected with combined mesopores and macropores because of a good SiO2 dispersion. Composite electrolyte membranes were prepared by soaking these porous nanofiber membranes in 1 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1 vol%). It is found that 12 wt% SiO2/PAN electrolyte membrane has the highest conductivity (1.1 × 10−2 S cm−1) due to the large liquid electrolyte uptake (about 490%). In addition, the electrochemical performance of composite electrolyte membranes is also improved after the introduction of SiO2. For initial cycle, 12 wt% SiO2/PAN composite electrolyte membrane delivers the discharge capacity of 139 mAh g−1 as 98% of theoretical value, and still retains a high value of 127 mAh g−1 as 89% at 150th cycle, which is significantly higher that of pure PAN nanofiber-based electrolyte membranes. 相似文献
19.
Preben J.S. Vie 《Electrochimica acta》2004,49(7):1069-1077
We report measured temperatures inside the single polymer fuel cell, and thermal conductivities and heat transfer coefficients calculated from these. Temperatures were measured next to the membrane on its two sides, and in the gas channels. Higher temperatures (5 °C or more at 1 A/cm2) were found at the membrane electrode surface than in the gas channels. The thermal conductivity of the membrane (λm) was small, as expected from the properties of water and polymer, while the heat transfer coefficient of the electrode surfaces (λs) was smaller, 1000±300 W/m2 K for a layer thickness of 10 μm. The real coefficient is smaller, since the measured temperatures are systematically smaller than the real ones. The electrode surface heat transfer coefficient is not previously reported. The average value for the catalyst surface plus gas diffusion layer was 0.2 W/m K. 相似文献
20.
Luis Gustavo S. Pereira 《Electrochimica acta》2006,51(19):4061-4066
The performance of proton exchange membrane fuel cells (PEMFC) fed with CO-contaminated hydrogen was investigated for anodes with PtWOx/C and phosphotungstic acid (PTA) impregnated Pt/C electrocatalysts. A quite high performance was achieved for the PEMFC fed with H2 + 100 ppm CO with anodes containing 0.4 mg PtWOx cm−2 and also for those with 0.4 mg Pt cm−2 impregnated with ca. 1 mg PTA cm−2. A decay of the single cell performance with time is observed, and this was attributed to an increase of the membrane resistance due to the polymer degradation promoted by the crossover of the tungsten species throughout the membrane. 相似文献