Hydrogen storage in amine boranes: Ionic liquid supported thermal dehydrogenation of ethylene diamine bisborane

A variety of ionic liquids has been tested for its catalytic effect on the dehydrogenation of ethylene diamine bisborane (EDB). The catalytic activity of ionic liquids, such as 1-butyl-2,3-dimethylimidazolium chloride ([BMMIM]Cl), 1-butyl-2,3-dimethylimidazolium acetate ([BMMIM][OAc]), 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]) and 1-butyl-3-methylimidazolium methylsulfonate ([BMIM][OMs]) is compared and the mixture [BMMIM]Cl/EDB was investigated. This system is able to deliver about 6.5 wt% of hydrogen at 140 °C competing with conventional hydrogen storage pressure tanks. The correlation between polarity of the ILs and hydrogen yield was investigated and the suitability for hydrogen storage systems is evaluated and discussed.     

Performance of PEMFC with new polyvinyl-ionic liquids based membranes as electrolytes

Polymer Electrolyte Membrane Fuel Cells (PEMFC) represent a key technology for sustainable energy production due to their high efficiency and low environmental impact. The use of task specific protic ionic liquids as electrolytes is gaining interest due to their high conductivity and thermal and electrochemical stability under anhydrous conditions. Ionic liquids with the imidazolium cation exhibit a high electrochemical stability, besides sulfonic groups can be incorporated to the cation as side chains acting as carriers in order to facilitate the proton transport. Moreover suitable anions such as Tf₂N and OTf provide high ionic conductivity. In this work, two different types of membranes based on protic ionic liquids have been tested in PEMFC under anhydrous conditions i) Nafion membranes impregnated with the protic ionic liquids 1-methyl-3-(4-sulfobutyl)-imidazolium bis(trifluoromethylsulfonyl)-imide ([HSO₃-BMIm][NTf₂]) and 1-butyl-3-(4-sulfobutyl)-imidazolium trifluoromethanesulfonate ([HSO₃-BBIm][OTf]) and, ii) membranes based on the polymerization of the specifically designed ionic liquid 1-(4-sulfobutyl)-3-vinylimidazolium trifluoromethanesulfonate ([HSO₃-BVIm][OTf]). The influence of different operation variables such as cell temperature, gas humidity and membrane thickness on the performance of the PEMFC has been analyzed, and the resistance exerted by the electrolyte was determined using electrical impedance spectroscopy. Nafion membranes impregnated with [HSO₃-BBIm][OTf] achieve current densities of 217 mA/cm² under anhydrous conditions at 25 °C whereas [HSO₃-BVIm][OTf] polymerized electrolytes provide current densities of 154 mA/cm² at the same conditions. This is the first report that describes the application of designed polymerized protic ionic liquids membranes for fuel cells. Although some improvements in terms of thermal and mechanical stability should be achieved, this first approach presents a promising electrolyte with challenging characteristics.     

Electropolymerization of high stable poly(3,4-ethylenedioxythiophene) in ionic liquids and its potential applications in electrochemical capacitor

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been successfully electropolymerized using a purified 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) as both the growth medium and the supporting electrolyte. The electrochemical performance of the PEDOT thin film was investigated in 1 mol L⁻¹ H₂SO₄ solution. It possesses nearly ideal capacitive property, and its specific capacitance is about 130 F g⁻¹. Compared with other conducting polymers, enhanced cycling lifetime (up to 70,000 cycles), which is close to that of active carbon materials, was observed on repetitive redox cycling.     

The effect of imidazolium ionic liquid on the morphology of Pt nanoparticles deposited on the surface of SrTiO3 and photoactivity of Pt–SrTiO3 composite in the H2 generation reaction

Photocatalytic water splitting has great potential in solar-hydrogen production as a low-cost and environmentally friendly method. Different unique techniques used to obtain photocatalysts with various modifications to improve H₂ generation have been introduced. In the present work, SrTiO₃ was successfully synthesized via the solvothermal method in the presence of ionic liquid (IL) - 1-butyl-3-methylimidazolium bromide ([BMIM][Br]) followed by surface decoration with Pt particles using the photodeposition method. The effect of the noble metal content and presence of IL on the morphology, optical and surface properties of SrTiO₃, thereby the effectiveness of hydrogen generation, has been thoroughly examined and presented. Unexpectedly, the presence of [BMIM][Br] at the SrTiO₃ surface affected the interaction between the semiconductor surface and platinum particles formed throughout photodeposition. Platinum particles at the surface of SrTiO₃_IL were found to be in the form of 2D clusters with a size of 1 nm. In comparison, Pt deposited on SrTiO₃ photocatalyst without application of IL created larger, three-dimensional structures with a diameter exceeding 5 nm. This is the reason why the total amount of platinum deposited on the SrTiO₃_IL sample is smaller than that on SrTiO₃ and justifies a higher efficiency of hydrogen generation of Pt modified SrTiO₃ photocatalyst in comparison to SrTiO₃ prepared in the presence of IL. The mechanism of H₂ generation in the water-splitting reaction in the presence of SrTiO₃_Pt photocatalyst was discussed.     

Ionic liquids in proton exchange membrane fuel cells: Efficient systems for energy generation

Proton exchange membrane fuel cells (PEMFCs) are used in portable devices to generate electrical energy; however, the efficiency of the PEMFC is currently only 40%. This study demonstrates that the efficiency of a PEMFC can be increased to 61% when 1-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF₄) ionic liquid (IL) is used together with the membrane electrode assembly (MEA). The results for ionic liquids (ILs) 1-butyl-3-methylimidazolium chloride (BMI.Cl) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF₄) in aqueous solutions are better than those obtained with pure water. The current and the power densities with IL are at least 50 times higher than those obtained for the PEMFC wetted with pure water. This increase in PEMFC performance can greatly facilitate the use of renewable energy sources.     

Polymer-supported 1-butyl-3-methylimidazolium trifluoromethanesulfonate and 1-ethylimidazolium trifluoromethanesulfonate as electrolytes for the high temperature PEM-type fuel cell

Membranes were prepared by casting a solution of a polymer and 1-butyl-3-methylimidazolium trifluoromethanesulfonate or 1-ethylimidazolium trifluoromethanesulfonate as typical representatives of aprotic and protic ionic liquids and then evaporating the solvent. The following two polymers were used: poly(vinylidene fluoride-co-hexafluoropropene) and Nafion. The prepared membranes were tested with respect to their ionic conductivity in dependence on temperature under dry conditions and under humidification. Subsequently, selected membranes were tested in a laboratory fuel cell. Whereas satisfactory ionic conductivity was observed for the prepared membranes, temperatures above 100 °C resulted in a low output performance of the fuel cell for all membrane materials under study. The main reason proposed for this is the low MEA conductivity for hydrogen ions.     

Ionic liquid based absorption chillers for usage of low grade waste heat in industry

The standard working pairs for absorption chillers, ammonia/water and water/lithium bromide show problematic behaviours like crystallisation and corrosiveness. Because of their convenient solving properties and their low vapour pressure, ionic liquids are a new promising class of sorbents for absorption cooling purposes. In this study, the working pairs water/1,3‐dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and water/1‐ethyl‐3‐methylimidazolium dimethylphosphate ([EMIM][DMP]) are implemented in AspenPlus. The performance of a single effect cycle with these pairs is simulated and compared to results of a cycle with water/LiBr. For [EMIM][DMP] a coefficient of performance (COP) comparable to that of LiBr or even higher (up to 0.85) is found. [MMIM][DMP] shows a smaller maximum COP but a largely wider operating temperature range than LiBr. Results are compared with those of other groups, discrepancies discussed and improvements suggested. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation of biohydrogen production from glucose and protein at neutral initial pH

Organic wastes are considered as potential substances for economical biohydrogen production, because the carbohydrate and protein are main components. Previous investigations indicate that an optimum hydrogen production appear in acidic conditions to carbohydrates, or in alkali condition to protein. However, in practice, the treatment of these organic wastes by anaerobic fermentation usually carries out at neutral pH condition, in which biohydrogen production is only a middle process. So, the purpose of this paper is to evaluate the biohydrogen production at neutral pH condition from carbohydrates or protein. Batch tests were conducted to investigate the differences in biohydrogen production by anaerobic fermentation at neutral initial pH using carbohydrate and protein (glucose and peptone) as the sole carbon source. The experimental results showed that the maximal hydrogen yields of two substrates were about 0.14 ml H₂/mg glucose and 0.077 ml H₂/mg protein, respectively, at neutral initial pH. Although the hydrogen yields of glucose is far greater than that of protein at neutral pH, they were lower than previous results of hydrogen production in acidic condition to carbohydrate or in alkali condition to protein. This result shows that the neutral pH is not an optimal condition for biohydrogen production. In this experiment of biohydrogen production, a phenomenon has been observed that the hydrogen production and hydrogen consumption occurred simultaneously in the fermentation of protein, whereas the hydrogen production occurred only in the fermentation of glucose. Furthermore, the different evaluation of the main components of the organic liquid by-products produced by fermentation of each substrate implied that the biohydrogen production pathways of these two substrates were different. Molecular analysis indicated that the dominant microorganisms during the anaerobic fermentation of these two substrates are greatly different.     

Boosting electrocatalysis of oxygen reduction and evolution reactions with cost-effective cobalt and nitrogen-doped carbons prepared by simple carbonization of ionic liquids

Development of cost-effective, bi-functional carbon electrocatalysts via direct carbonization of ionic liquids (bis(cholinium) tetrachlorocobaltate(II) ([Ch]₂[CoCl₄]) and bis(1-butyl-3-methylimidazolium) tetrachlorocobaltate(II) ([Bmim]₂[CoCl₄])) is reported herein for the first time. Carbon electrocatalysts, dual-doped with cobalt and nitrogen, were tested for oxygen reduction (ORR) and oxygen evolution (OER) reactions. Both materials show high bi-functional catalytic activity and excellent stability due to synergistic effects arising from the presence of nitrogen and cobalt. Electrocatalyst prepared by carbonization of [Ch]₂[CoCl₄] show exceptional activity and selectivity toward ORR. Conversely, electrocatalyst prepared from [Bmim]₂[CoCl₄] showed a slightly better OER performance indicating that different catalytic sites are responsible for O₂ reduction and H₂O oxidation. Parent CoO particles with graphitic nitrogen boost activity for ORR, while elemental Co supported by nitrogen atoms is responsible for OER activity. Finally, energy consumption during electrolytic oxygen production was calculated revealing energy saving when using two materials as anode electrocatalysts.     

Characterization of ionic liquid pretreatment and the bioconversion of pretreated mixed softwood biomass

In this study, mixed softwoods were pretreated with an ionic liquid, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), and the bioconversion efficiencies to fermentable sugars were estimated through the enzymatic hydrolysis. The cellulose crystallinity, surface morphology, structures and compositions of softwood were significantly changed after the ionic liquid pretreatment was carried out under a wide range of temperatures and reaction times. And, biomass digestibility significantly increased with increasing pretreatment temperature and reaction time. The enzymatic degradation of pretreated softwoods was remarkably improved at the pretreatment of high temperatures via the modification of crystalline cellulose I to a mixture of easily digestable cellulose II and amorphous structure, and partial removal of hemicellulose. The conversion of cellulose to glucose reached more than 90% at relevant conditions and the highest glucose yield was measured to about 78%. Through the study, it was clearly shown that ionic liquid pretreatment is one of the effective methods to produce high fermentable sugars without lignin dissolution from lignocellulosic biomass.     

Multi-Effect Plants and Ionic Liquids for Improved Absorption Chillers

State-of-the-art absorption chillers using conventional working pairs still suffer from problems like crystallization, corrosiveness, and a relatively low efficiency. To improve this technology, different working pairs as well as plant designs are investigated using the simulation tool AspenPlus. The simulation is validated by comparing the results of single-effect absorption chillers using the current commercially applied working pairs water/lithium bromide and ammonia/water with literature data. To increase the efficiency, double-effect absorption chillers are implemented and analyzed. The performance of two kinds of double-effect cycles, series and parallel, is compared using the working pair water/lithium bromide. In addition, ionic liquids (ILs) are investigated as a sorbent in order to improve the technology. So far, ILs have not been implemented in AspenPlus yet. Therefore, a guideline for the implementation of ILs in AspenPlus is outlined and the accordant phase equilibria results are validated with literature data. Simulations of single-effect cycles using the ILs 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM][DMP]) in combination with water as a refrigerant are performed and the results are compared to conventional working pairs. It is shown that by using ILs, similar or even higher coefficients of performance (COPs) can be achieved in comparison to conventional working pairs. Moreover, the findings reveal that the main benefit of using ILs as a sorbent consists in providing a broader operating range with respect to heat source temperature.     

Brønsted酸性离子液体合成及催化制备生物柴油

合成4种成功能化酸性离子液体,采用红外光谱、热重分析等分析法进行表征验证,并用其催化菜籽油酯交换制备生物柴油,考察醇/油物质的量之比、反应温度、反应时间、离子液体用量和水含量对转化率的影响。结果表明,4种离子液体都有较强酸性,与浓硫酸酸性相当;带—SO₃H基团的离子液体表现出更好的催化活性,且随着烷基链的增加,催化活性提高;在（n甲醇）∶n（菜籽油）=12∶1,反应温度130 ℃,反应时间3 h,离子液体（[BSO₃HMIM][HSO₄]）用量为菜籽油质量2%（质量分数）条件下,生物柴油转化率可达99%以上。在反应体系中,水会破坏离子液体的结构并导致其失活,而升高反应温度,可缓解水对离子液体的结构破坏,在130 ℃条件下,即使水分含量为5%时,生物柴油转化率仍可保持在约85%。     

Measurements of thermal conductivity of 1‐butyl‐3‐methylimidazolium tetrafluoroborate at high pressure

Ionic liquids are salts that are liquid at room temperature. They have attracted considerable attention as new materials. In this study, a transient short‐hot‐wire apparatus was prepared, and the thermal conductivity of 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim] [BF₄]) was measured. The experimental temperatures were from 294 to 334 K, and the pressures were from 0.1 to 20 MPa. It was found that the thermal conductivity of an ionic liquid has a very small temperature and pressure dependence. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(6): 361–372, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20166     

Vapor–liquid equilibria of ammonia + ionic liquid mixtures

Solubilities of ammonia in room-temperature ionic liquids, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium ethylsulfate, and N,N-dimethylethanolammonium acetate have been measured for the first time. Static phase equilibrium cells used in our previous work have been slightly modified for the present solubility measurements. Six mixture compositions of each binary system were prepared for the present experiments from about 30 to 85 mol% of ammonia. Pressure–temperature–composition (PTx) data were measured at isothermal conditions of about 283, 298, 323, 348, and 373 K. Observed solubilities in the present ionic liquids are again very high, being similar to our previous report on ammonia + ionic liquid mixtures and all cases show negative deviations from ideal solution behavior. Experimental PTx data have been successfully correlated with our equation-of-state (EOS) model. All the excess properties (enthalpy, entropy, and Gibbs energy) show negative values, indicating some intermolecular complex formation between ammonia and ionic liquids. Application of the present systems to the absorption cooling–heating cycle has also been discussed.     

Biohydrogen from complex carbohydrate wastes as feedstocks—Cellulose degraders from a unique series enrichment

Fermentative biohydrogen production is a particularly promising approach offering high hydrogen yields and fast rates. Its drawback is that it uses mono- and disaccharides for substrates and these are relatively expensive. However, more complex carbohydrates may be converted to the feedstocks for fermentative biohydrogen production using approaches derived from select organisms. Early data from a consortium with cellulolytic activity recovered from aerobic thermophilic swine waste product and sequentially selected with batch operation on distiller's dry grain (a product of dry grind ethanol manufacture) has been used as a source of inoculum. Mesophilic and thermophilic cellulose-degrading organisms have been isolated from this inoculum and are reported here. Work continues on further characterization of these organisms and their potential. This work will be considered in light of an organizational scheme of processes using aerobic or anaerobic as well as mesophilic or thermophilic organisms. Some literature examples will be discussed. It is possible that these organisms could be used in a saccharification/fermentation process using separate reactors or a single reactor with coimmobilized cells providing both aerobic saccharification and anaerobic hydrogen fermentation.     

Proton conduction of novel calcium phosphate nanocomposite membranes for high temperature PEM fuel cells applications

This work describes the synthesis and evaluation of nanocomposite membranes based on calcium phosphate (CP)/ionic liquids (ILs) for high-temperature proton exchange membrane (PEM) fuel cells. Several composite membranes were synthesized by varying the mass ratios of ILs with respect to the CP and all supported on porous polytetrafluoroethylene (PTFE). The membranes exhibit high proton conductivities. Two ionic liquids were investigated in this study, namely, 1-Hexyl-3- methylimidazolium tricyanomethanide, [HMIM][C₄N₃⁻], and 1-Ethyl-3-methylimidazolium methanesulfonate, [EMIM][CH₃O₃S⁻]. At room temperature, the CP/PTFE/[HMIM][C₄N₃⁻] composite membrane possessed a high proton conductivity of 0.1 S cm⁻¹. When processed at 200 °C, and fully anhydrous conditions, the membrane showed a conductivity of 3.14 × 10⁻³ S cm⁻¹. Membranes based on CP/PTFE/[EMIM][CH₃O₃S⁻] on the other hand, had a maximum proton conductivity of 2.06 × 10⁻³ S cm⁻¹ at room temperature. The proton conductivities reported in this work appear promising for the application in high-temperature PEMFCs operated above the boiling point of water.     

Strategies for improvement of biohydrogen production from organic-rich wastewater: A review

Biohydrogen can be produced from organic wastewater but the process is limited by low production yields. The aim of this review is to summarize the production strategies which are recently researched for enhancing biohydrogen yield and productivity from organic wastewater. The survey of published work indicates that the dark hydrogen fermentation is the most promising production mode. Current strategies geared towards improving biohydrogen production include: microbial culture immobilization, bioreactor modifications, the optimization of process conditions (temperature, pH, OLR and HRT), culture selection and enrichments, substrate choice, and the metabolic engineering of biohydrogen specialists. Comparative analysis of energy recovery from anaerobic digestion using vinasse-related substrates indicates that the production of methane has a higher energy yield than production of hydrogen. A sequential combination of biohydrogen and biomethanation production phases has the potential for even higher bioenergy recovery from organic wastewater.     

A multi-criteria decision making analysis for feasibility of nanoparticle addition in biohydrogen production enhancement for scaling-up studies

Nanoparticles (NPs) thanks to their unique features such as large surface area, high catalytic activity and intra-cellular electron transfer ability used as an enhancement additive in biohydrogen production. Up to date, inorganic, organic and their mixtures of various NPs were produced from different input sources and synthesis methodology. The NPs properties and cost minimization are the critical factors for the scale up studies of industrial applications. Nevertheless, there have not been any study on the determination of the most efficient and feasible NPs in biohydrogen production for the scaling up the process. In this study, the NPs used for biohydrogen production enhancement over Clostridium sp. by dark fermentation were examined and these studies were evaluated to determine the most effective and feasible NPs using the two-stage TOPSIS method. As a result, iron-containing NPs (hematite, magnetite) were determined as the most effective and economical NPs for increasing the yield.     

Evaluation of the biogas potential of mucilage formed in the Marmara Sea

The mucilage, which emerged as a result of increasing global warming and the deterioration of marine ecosystem balances, has taken the Marmara Sea under its influence. Mucilage appears in some periods and there is not much information about its bioenergy production potential. In this study, the biogas and biohydrogen production potential was determined when mucilage collected from the coasts is used as a substrate. Different S/X ratios were evaluated for biogas production. The highest biogas production was observed as 682 ml/g VS at the S/X ratio of 2. Dark fermentation was carried out using mixed Clostridium sp. to produce biohydrogen. As a result of fermentation, a maximum biohydrogen yield of 117 ml H₂/g VS hydrogen was obtained. In terms of both biogas and hydrogen results, the bioenergy potentials of the mucilage sample taken from the surface were determined to be higher than the bottom sediment.     

Biohydrogen yield efficiency and the benefits of dark,photo and dark-photo fermentative production technology in circular Asian economies

Twenty-six new data envelopment analysis (DEA) models with 55 biohydrogen production experiments categorized into three groups including dark fermentation (DF), photo fermentation (PF), and dark-photo sequential fermentation (DF-PF) technologies, are used to evaluate their biohydrogen yield efficiency. The results reveal the average yield efficiencies of DF, PF and DF-PF are 0.2844, 0.3460 and 0.7040, respectively. The most efficient overall combination of biohydrogen inputs is PhBR1/Rhodobacter capsulatus B10/Rhodobacter capsulatus in DF-PF. Statistical tests demonstrate DF-PF has statistically double the efficiency of PF and DF, and the efficiency of PF significantly exceeds that of DF, supporting some of the literature findings. A flexible DEA model must be carefully chosen when evaluating biohydrogen production. All inputs and outputs of biohydrogen statistically influenced yield efficiency to a significant level. India and Japan are the top two economies benefitting from improved biohydrogen yield efficiency. Improving biohydrogen yield efficiency can improve macroeconomic growth and develop the renewable hydrogen and biohydrogen industry.