New polymer electrolyte membrane for medium-temperature fuel cell applications based on cross-linked polyimide Matrimid and hydrophobic protic ionic liquid

New hydrophobic protic ionic liquid, 2-butylaminoimidazolinium bis(trifluoromethylsulfonyl)imide (BAIM-TFSI), has been synthesized. The ionic liquid showed good thermal stability to at least 350 °C. The conductivity of BAIM-TFSI determined by electrochemical impedance method was found to be 5.6 × 10^?2 S/cm at 140 °C. Homogeneous composite films based on commercial polyimide (PI) Matrimid and BAIM-TFSI containing 30–60 wt% of ionic liquid were prepared by casting from methylene chloride solutions. Thermogravimetric analysis data indicated an excellent thermal stability of PI/BAIM-TFSI composites and thermal degradation points in the temperature range 377 °C–397 °C. The addition of ionic liquid up to 50 wt% in PI films does not lead to any significant deterioration of the tensile strength of the polymer. The dynamic mechanical analysis results indicated both an increase of storage modulus E′ of PI/BAIM-TFSI composites at room temperature and a significant E′ decrease with temperature compared with the neat polymer. The cross-linking of the PI with polyetheramine Jeffamine D-400 allowed to prepare PI/Jeffamine/BAIM-TFSI (50%) membrane with E′ value of 300 MPa at 130 °C. The ionic conductivity of this cross-linked composite membrane reached the level of 10^?2 S/cm at 130 °C, suggesting, therefore, its potential use in medium-temperature fuel cells operating in water-free conditions.     

Fabrication and characterization of supported dual acidic ionic liquids for polymer electrolyte membrane fuel cell applications

In this study, we proposed an innovative and versatile method for preparation of highly stable and conductive supported ionic liquid (IL) membranes for proton exchange fuel cell applications. Novel covalently supported dual acidic IL membranes were prepared by radiation induced grafting of 4-vinyl pyridine (4-VP) onto poly(ethylene-co-tetrafluoroethylene) (ETFE) film followed by post-functionalization via sequential treatments with 1,4-butane sultone and sulfuric acid to introduce pyridinium alkyl sulfonate/hydrogen sulfate moieties. The advantage of our approach lies in grafting polymers with highly reactive functional groups suitable for efficient post-sulfonation. The membranes displayed better swelling and mechanical properties compared to Nafion 112 despite having more than 3 times higher ion exchange capacity (IEC). The proton conductivity reached superior values to Nafion above 80 °C. Particularly, the membrane with ion exchange capacity of 3.41 displayed a proton conductivity of 259 mScm⁻¹ at 95 °C. This desired conductivity value is attributed to the high IEC of the membranes as well as dissociation of the hydrophobic ETFE polymer and hydrophilic pyridinium alkyl sulfonate groups. Such appealing properties make the supported IL membranes promising for proton exchange membrane fuel cells (PEMFC).     

Reinforced and self-humidifying composite membrane for fuel cell applications

A novel preparation method for a composite proton exchange membrane with reinforced strength and self-humidifying property was developed. Using self-assembly method, highly dispersed poly(diallyldimethylammonium chloride) (PDDA) stabilized Pt nanoparticles were mounted onto the pores of poly(tetrafluoroethylene) (PTFE) porous film to serve the self-humidifying purpose. With Pt nanoparticles fixed on the PTFE pores, the potential problem of any short circuit because of the use of metal nanoparticles can be prevented. Pt-PDDA/PTFE substrate in the composite membrane can enhance the mechanical strength of the membrane and distribute self-humidifying layer adjacent to the anode side. Compared with the cells fabricated with conventional Nafion^® and PTFE/Nafion membranes, the performance of the cells with this composite membrane is dramatically improved under dry conditions. Electrochemical impedance spectroscopy technique revealed that these self-humidifying composite membranes could minimize membrane conductivity loss under dry conditions.     

Ionic liquid/ionic liquid dispersive liquid-liquid microextraction

In this article, a novel and simple microextraction method, termed ionic liquid/ionic liquid dispersive liquid–liquid microextraction (IL/IL‐DLLME), has been designed and developed for the rapid enrichment and analysis of environmental pollutants. Instead of using hazardous organic solvents, two kinds of ILs, hydrophobic IL and hydrophilic IL, were used as extraction solvent and disperser solvent in IL/IL‐DLLME step, respectively. Permethrin and biphenthrin, two of the often‐used pyrethroid pesticides, were used as model compounds. Factors that may affect the enrichment efficiencies were investigated and optimized in detail. Under optimum conditions, permethrin and biphenthrin exhibited a wide linear relationship over the range 1–100 μg/L. For permethrin and biphenthrin, the precisions were 4.65–7.78%, and limits of detection were found to be 0.28 and 0.83 μg/L, respectively. Satisfactory results were achieved when the present method was applied to analyze the target compounds in real‐world water samples with spiked recoveries over the range 84.1–113.5%. All these facts indicated that IL/IL‐DLLME is a simple and rapid alternative for the enrichment and analysis of environmental pollutants and will have a wide application perspective in the future.     

Sulfonated multiblock copoly(ether sulfone)s as membrane materials for fuel cell applications

Arylene ether multiblock copolymers of the (AB)_n-type with various degrees of sulfonation have been prepared by a two-step polycondensation procedure. Multiblock copolymers in high yields and of high molecular weights were obtained. For comparison random copolymers with the same overall composition were synthesized. The theoretical ion-exchange capacities (IEC) of the materials were ranging from 0.50 mmol/g to 1.25 mmol/g. The water-uptake of the multiblock copolymers showed a linear dependency from the IEC and was increasing with increasing IEC. No differences were observed between random and block copolymers. Furthermore, the hydrolytic stability of aromatic sulfonic acid groups was investigated in this study. Aromatic sulfonic acids, having additional electron donating groups, especially in ortho- or para-position to the sulfonic acid group are sensitive to hydrolytic desulfonation. On the other hand electron-withdrawing groups in meta-position showed a stabilizing effect.     

Combination of ionic liquid dispersive liquid-phase microextraction and high performance liquid chromatography for the determination of triazine herbicides in water samples

A temperature-controlled ionic liquid dispersive liquid-phase microextraction in combination with high performance liquid chromatography was developed for the enrichment and determination of triazine herbicides such as cyanazine,simazine,and atrazine in water samples.1-Octyl-3-methylimidazolium hexafluorophosphate([C8MIM][PF6]) was selected as the extraction solvent.Several experimental parameters were optimized.Under the optimal conditions,the linear range for cyanazine was in the concentration range of 0.5–80 mg/L and the linear range for simazine and atrazine was in the range of1.0–100 mg/L.The limit of detection(LOD,S/N = 3) was in the ranges of 0.05–0.06 mg/L,and the intra day and inter day precision(RSDs,n = 6) was in the ranges of 3.2%–6.6% and 4.8%–8.9%,respectively.Four real water samples were analyzed with the developed method,and the experimental results showed that the spiked recoveries were satisfactory.All these exhibited that the developed method was a valuable tool for monitoring such pollutants.     

Morphology-controlled synthesis of nanostructured zinc hydroxide fluoride via a microwave-assisted ionic liquid route

Zinc hydroxide fluoride (Zn(OH)F) with multiform morphologies such as flower-like particles, pumpkin-like aggregates, and hollow orange-like aggregates are prepared by a microwave-assisted ionic liquid method. During synthesis, microwave irradiation accelerates the reaction rate and shortens the reaction time. 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF₄]) or 1-2-hydroxylethyl-3-methylimidazolium tetrafluoroborate ([C₂OHmim][BF₄]) is used as both reactant and template. Experimental results indicate that the morphology evolution of Zn(OH)F is mainly controlled by the concentration of zinc acetate solution. A possible mechanism underlying the formation of nanostructured Zn(OH)F with diverse morphologies is proposed. Furthermore, nanoporous ZnO is obtained by the thermal decomposition of as-prepared Zn(OH)F in air, and the morphology is well retained.     

Ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction for the separation and determination of estrogens in water samples by high‐performance liquid chromatography with fluorescence detection

An ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction method was proposed for the extraction and concentration of 17‐α‐estradiol, 17‐β‐estradiol‐benzoate, and quinestrol in environmental water samples by high‐performance liquid chromatography with fluorescence detection. 1‐Hexyl‐3‐methylimidazolium tetrafluoroborate was applied as foaming agent in the foam flotation process and dispersive solvent in microextraction. The introduction of the ion‐pairing and salting‐out agent NH₄PF₆ was beneficial to the improvement of recoveries for the hydrophobic ionic liquid phase and analytes. Parameters of the proposed method including concentration of 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, flow rate of carrier gas, floatation time, types and concentration of ionic liquids, salt concentration in samples, extraction time, and centrifugation time were evaluated. The recoveries were between 98 and 105% with relative standard deviations lower than 7% for lake water and well water samples. The isolation of the target compounds from the water was found to be efficient, and the enrichment factors ranged from 4445 to 4632. This developing method is free of volatile organic solvents compared with regular extraction. Based on the unique properties of ionic liquids, the application of foam floatation, and dispersive liquid–liquid microextraction was widened.     

Ionic cyclodextrins in ionic liquid matrices as chiral stationary phases for gas chromatography

Ionic liquids (ILs) are used to dissolve ionic cyclodextrin (CD) derivatives to produce a new type of gas chromatographic chiral stationary phase. Compared to a previous study with neutral cyclodextrin chiral selectors, the new ionic liquid-based stationary phase exhibits broader enantioselectivities, up to seven times higher efficiencies, and greater thermal stabilities. When compared to the analogous commercial column with polysiloxane matrix, it exhibits different enantioselectivities, more symmetric peak shapes and some complementary enantioseparations. The most profound separation enhancements are usually found for more polar analytes.     

咪唑类离子液体用作电解质对燃料电池性能的影响

为优化改善燃料电池的整体性能,在自由电解质燃料电池中,考察了五种咪唑类离子液体用作燃料电池电解质时对燃料电池性能的影响。结果表明,以氢气为燃料时,在相同电流密度下,电路电压和输出功率从高到低依次为1-丁基-3-甲基咪唑四氟硼酸盐 > 1-丁基-3-甲基咪唑六氟磷酸盐 > 氢氧化钠溶液 >> 氯化-1-丁基-3-甲基咪唑 > 溴化-1-丁基-3-甲基咪唑 > 1-丁基-3-甲基咪唑硫酸氢盐;以甲烷为燃料时,相同电流密度下,电路电压和输出功率从高到低则依次为溴化-1-丁基-3-甲基咪唑 > 1-丁基-3-甲基咪唑硫酸氢盐 > 氯化-1-丁基-3-甲基咪唑 > 氢氧化钠溶液> 1-丁基-3-甲基咪唑四氟硼酸盐 > 1-丁基-3-甲基咪唑六氟磷酸盐。以[Bmim]BF₄为氢气燃料电池电解质时,温度升高和离子液体中水含量增加,均会使燃料电池的性能减弱。     

Determination of phthalate esters in water samples by ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography

A novel method, termed ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction (IL-CIA-DLLME), combined with high-performance liquid chromatography (HPLC) was developed for the determination of three phthalate esters in water samples. Several important parameters influencing the IL-CIA-DLLME extraction efficiency, such as the type of extraction and disperser solvent, the volume of extraction and disperser solvent, temperature, extraction time and salt effect, were investigated. Under optimal extraction conditions, the enrichment factors and extraction recoveries ranged from 174 to 212 and 69.9 to 84.8%, respectively. Excellent linearity with coefficients of correlation from 0.9968 to 0.9994 was observed in the concentration range of 2–100 ng mL⁻¹. The repeatability of the proposed method expressed as relative standard deviations ranged from 2.2 to 3.7% (n = 5). Limits of detection were between 0.68 and 1.36 ng mL⁻¹. Good relative recoveries for phthalate esters in tap, bottled mineral and river water samples were obtained in the ranges of 91.5–98.1%, 92.4–99.2% and 90.1–96.8%, respectively. Thus, the proposed method has excellent potential for the determination of phthalate esters in the environmental field.     

Selenonium ionic liquid as efficient catalyst for the Baylis-Hillman reaction

The new acidic ionic liquid phenyl butyl ethyl selenonium tetrafluoroborate, [pbeSe]BF₄, was successful used as a co-catalyst in the Baylis-Hillman reaction of aldehydes and electron-deficient alkenes. The Baylis-Hillman adducts were obtained in moderated to good yields and in relatively short reaction times under mild conditions.     

Solvatochromic parameters for binary mixtures of an ionic liquid with various protic molecular solvents

Abstract  Solvatochromic parameters (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) have been determined for binary mixtures of propan-2-ol, propan-1-ol, ethanol, methanol and water with recently synthesized ionic liquid (IL; 2-hydroxyethylammonium formate) at 25 °C. In all solutions except aqueous solution, E _T ^N values of the media increase abruptly with the ILs mole fraction and then increase gradually to the value of pure IL. A synergistic behavior is observed for the α parameter in all solutions. The behavior of π* and β are nearly ideal for all solutions except for solutions of methanol with the IL. The applicability of nearly ideal combined binary solvent/Redlich–Kister equation was proved for the correlation of various solvatochromic parameters with solvent composition. The correlation between the calculated and the experimental values of various parameters was in accordance with this model. Solute–solvent and solvent–solvent interactions were applied to interpret the results. Graphical Abstract  Predicted values of solvatochromic parameters (SP) (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) from the correlation equations versus its experimental values for binary mixtures of 2-hydroxyethylammonium formate with water, methanol, ethanol, propan-1-ol and propan-2-ol.      

Structure and morphology controllable synthesis of Ag/carbon hybrid with ionic liquid as soft-template and their catalytic properties

Ag/carbon hybrids were fabricated by the redox of glucose and silver nitrate (AgNO₃) in the presence of imidazolium ionic liquid ([C₁₄mim]BF₄) under hydrothermal condition. Monodisperse carbon hollow sub-microspheres encapsulating Ag nanoparticles and Ag/carbon cables were selectively prepared by varying the concentration of ionic liquid. Other reaction parameters, such as reaction temperature, reaction time and the mole ratio of silver nitrate to glucose, play important roles in controlling the structures of the products. The products were characterized by XRD, TEM (HRTEM), SEM, energy-dispersive X-ray spectroscopy (EDX), FTIR spectroscopy and a Raman spectrometer. The possible formation mechanism was proposed. The catalytic property of the hybrid in the oxidation of 1-butanol by H₂O₂ was also investigated.     

Direct methanol fuel cells for vehicular applications

Dramatic technological advances for the proton exchange membrane fuel cell have focused attention on this technology for motor vehicles. The fuel cell vehicles (FCVs) have the potential to compete with the petroleum-fueled internal combustion engine vehicles (ICEVs) in cost and performance while effectively addressing air quality, energy insecurity, and global warming concerns. Methanol being a liquid can be easily transported and can be supplied from the existing network of oil company distribution sites. Recently, combining improved catalysts with fuel cell engineering, it has been possible to overcome some of the difficulties that have frustrated previous research and development efforts in realizing a commercially viable direct methanol fuel cell. Direct methanol fuel cells (DMFCs) with power densities between 0.2 and 0.4 W/cm² at operational temperatures in the range 95–130 °C have been developed. These power densities are sufficient to suggest that stack construction is well worth while. This paper reviews recent advances and technical challenges in the field of DMFCs. Received: 27 May 1997 / Accepted: 25 November 1997     

Performance assessment of a spiral methanol to hydrogen fuel processor for fuel cell applications

A novel design of plate-type microchannel reactor has been developed for fuel cell-grade hydrogen production.Commercial Cu/Zn/Al2O3 was used as catalyst for the reforming reaction,and its effectiveness was evaluated on the mole fraction of products,methanol conversion,hydrogen yield and the amount of carbon monoxide under various operating conditions.Subsequently,0.5 wt% Ru/Al2O3 as methanation catalyst was prepared by impregnation method and coupled with MSR step to evaluate the capability of methanol processor for CO reduction.Based on the experimental results,the optimum conditions were obtained as feed flow rate of 5mL/h and temperature of 250℃,leading to a low CO selectivity and high H2 yield.The designed reformer with catalyst coated layer was compared with the conventional packed bed reformer at the same operating conditions.The constructed fuel processor had a good performance and excellent capability for on-board hydrogen production.     

Crystallization behavior and biodegradation of poly(3-hydroxybutyrate) and poly(ethylene glycol) multiblock copolymers

Block copolymerization by using isocyanates is an effective method for incorporating PHB and PEG because it can prepare copolymers with good properties, such as toughness, strength, and so on. In this study, we adopted soil suspension system to estimate the biodegradability of a series of PHB/PEG multiblock copolymers with different compositions and block lengths. In the degradation process, the changes in weight loss, molecular weight, and tensile strength were periodically measured to determine the biodegradability, and the surface morphology was also observed by SEM. In contrast to pure PHB, the weight loss of the copolymer was relatively lower. On the other hand, the tensile strength and molecular weight experienced apparent decrease, and for BHG1000-3-1, they reached 46.7% and 77.7% of the initial value, respectively. SEM observation showed that the surface was covered with numerous erosion pits. All these indicate that the degradation indeed took place and long-chain molecules have been hydrolyzed into shorter ones. The crystallization behavior was also investigated by DSC and WAXD. The results showed that both the segments, PEG and PHB, can form crystalline phases at lower PHB contents ranging from 29% to 44%, and when PHB component was more than 60%, only PHB phase can crystallize.     

Synthesis and characterization of PLLA-PLCA-PEG multiblock copolymers and their applications in modifying PLLA porous scaffolds

Poly(l-lactic acid)-poly(l-lactic acid-co-citric acid)-poly(ethylene glycol) multiblock copolymers (PLLA-PLCA-PEG) were synthesized through polycondensation reaction and characterized by ¹H NMR and DSC. The three-dimensional ultrafine fibre microporous PLLA/PLLA-PLCA-PEG scaffolds were then fabricated by modifying PLLA with PLLA-PLCA-PEG through blending and characterized as well. Properties of scaffolds such as swelling and degradation behaviors, morphology and mechanical moduli were fully investigated. Tetrandrine-loaded PLLA/PLLA-PLCA-PEG scaffolds were also fabricated and their drug releasing behaviors were taken into consideration. Compressive testing research shows that the mechanical flexibility improves as the content of PLLA-PLCA-PEG copolymers in the scaffolds increases. The TED encapsulation efficiency of the scaffold is enhanced when the amount of PLLA-PLCA-PEG increases because of the acid-base interaction between carboxylic acid groups of the copolymer with TED. The releasing velocity of TED speeds up while the PLLA-PLCA-PEG blocks ratios in scaffolds increase. So modification of PLLA scaffold with PLLA-PLCA-PEG shall broaden its applications in tissue engineering.     

Electro- and acid-catalysis in tetrafluoroborate-based ionic liquid: new alternative routes for the oxidation of sulfides with UHP

By means of anodic activation, BF₄-based ionic liquid was found to play the triple role of electrolysis/reaction medium, supporting electrolyte and pre-catalyst versus the oxidation of sulfides with UHP. Galvanostatic electrolysis in the presence of substrate and UHP molecules allowed the fast, efficient and selective achievement of sulfoxides. Comparable results have been attained by acid catalysis based on R-CSA.     

Synthesis and characterization of multiblock copolymers based on hydrophilic disulfonated poly(arylene ether sulfone) and hydrophobic partially fluorinated poly(arylene ether ketone) for fuel cell applications

Sulfonated fluorinated multiblock copolymers based on high performance polymers were synthesized and evaluated for use as proton exchange membranes (PEMs). The multiblock copolymers consist of fully disulfonated poly(arylene ether sulfone) and partially fluorinated poly(arylene ether ketone) as hydrophilic and hydrophobic segments, respectively. Synthesis of the multiblock copolymers was achieved by a condensation coupling reaction between controlled molecular weight hydrophilic and hydrophobic oligomers. The coupling reaction could be conducted at relatively low temperatures (e.g., 105 °C) by utilizing highly reactive hexafluorobenzene (HFB) as a linkage group. The low coupling reaction temperature could prevent a possible trans‐etherification, which can randomize the hydrophilic‐hydrophobic sequences. Tough ductile membranes were prepared by solution casting and their membrane properties were evaluated. With similar ion exchange capacities (IECs), proton conductivity and water uptake were strongly influenced by the hydrophilic and hydrophobic block sequence lengths. Conductivity and water uptake increased with increasing block length by developing nanophase separated morphologies. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) experiments revealed that the connectivity of the hydrophilic segments was enhanced by increasing the block length. The systematic synthesis and characterization of the copolymers are reported. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 214–222, 2010