Energy storage in electrochemical capacitors: designing functional materials to improve device performance

Electrochemical capacitors, also known as supercapacitors, are becoming increasingly important components in energy storage, although their widespread use has not been attained due to a high cost/ performance ratio. Fundamental research is contributing to lowered costs through the engineering of new materials. Currently the most viable materials used in electrochemical capacitors are biomassderived and polymer-derived activated carbons, although other carbon materials are useful research tools. Metal oxides could result in a step change for electrochemical capacitor technology and is an exciting area of research. The selection of an appropriate electrolyte and electrode structure is fundamental in determining device performance. Although there are still many uncertainties in understanding the underlying mechanisms involved in electrochemical capacitors, genuine progress continues to be made. It is argued that a large, collaborative international research programme is necessary to fully develop the potential of electrochemical capacitors.

Effect of activated carbon xerogel pore size on the capacitance performance of ionic liquid electrolytes

The use of ionic liquid (IL) electrolytes promises to improve the energy density of electrochemical capacitors (ECs) by allowing for operation at higher voltages. Several studies have also shown that the pore size distribution of materials used to produce electrodes is an important factor in determining EC performance. In this research the capacitative, energy and power performance of ILs 1-ethyl-3- methylimidazolium tetrafluoroborate (EMImBF4), 1-ethyl-3-methylimidazolium dicyanamide (EMImN(CN)2), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPImTFSI), and 1-butyl-3-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMPyT(F5Et)PF3) were studied and compared with the commercially utilised organic electrolyte 1M tetraethylammonium tetrafluoroborate solution in anhydrous propylene carbonate (Et4NBF4–PC 1 M). To assess the effect of pore size on IL performance, controlled porosity carbons were produced from phenolic resins activated in CO2. The carbon samples were characterised by nitrogen adsorption– desorption at 77 K and the relevant electrochemical behaviour was characterised by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The best capacitance performance was obtained for the activated carbon xerogel with average pore diameter 3.5 nm, whereas the optimum rate performance was obtained for the activated carbon xerogel with average pore diameter 6 nm. When combined in an EC with IL electrolyte EMImBF4 a specific capacitance of 210 F g1 was obtained for activated carbon sample with average pore diameter 3.5 nm at an operating voltage of 3 V. The activated carbon sample with average pore diameter 6 nm allowed for maximum capacitance retention of approximately 70% at 64 mA cm2.

Oligomerisation of linear 1-olefins using a chlorogallate(III) ionic liquid

A Lewis acidic chlorogallate(III) ionic liquid, 1-ethyl-3-methylimidazolium hepta-chlorodigallate(III), [C(2)mim][Ga2Cl7], was successfully used to oligomerise 1-pentene. The influence of temperature, time, catalyst concentration, and stirring rate on conversion and product distribution was modelled using a design of experiment (DoE) approach (chemometrics). The process was optimised for lubricant base oils production; the C20-C50 fraction (where Cn indicates the number of carbons in the oligomer) was maximised, while the heavier oligomer fraction (>C50) was minimised.

Selective Orthosteric Free Fatty Acid Receptor 2 (FFA2) Agonists IDENTIFICATION OF THE STRUCTURAL AND CHEMICAL REQUIREMENTS FOR SELECTIVE ACTIVATION OF FFA2 VERSUS FFA3

Free fatty acid receptor 2 (FFA2; GPR43) is a G protein-coupled seven-transmembrane receptor for short-chain fatty acids (SCFAs) that is implicated in inflammatory and metabolic disorders. The SCFA propionate has close to optimal ligand efficiency for FFA2 and can hence be considered as highly potent given its size. Propionate, however, does not discriminate between FFA2 and the closely related receptor FFA3 (GPR41). To identify FFA2-selective ligands and understand the molecular basis for FFA2 selectivity, a targeted library of small carboxylic acids was examined using holistic, label-free dynamic mass redistribution technology for primary screening and the receptor-proximal G protein [S-35] guanosine 5'-(3-O-thio) triphosphate activation, inositol phosphate, and cAMP accumulation assays for hit confirmation. Structure-activity relationship analysis allowed formulation of a general rule to predict selectivity for small carboxylic acids at the orthosteric binding site where ligands with substituted sp(3)-hybridized alpha-carbons preferentially activate FFA3, whereas ligands with sp(2)- or sp-hybridized alpha-carbons prefer FFA2. The orthosteric binding mode was verified by site-directed mutagenesis: replacement of orthosteric site arginine residues by alanine in FFA2 prevented ligand binding, and molecular modeling predicted the detailed mode of binding. Based on this, selective mutation of three residues to their non-conserved counterparts in FFA3 was sufficient to transfer FFA3 selectivity to FFA2. Thus, selective activation of FFA2 via the orthosteric site is achievable with rather small ligands, a finding with significant implications for the rational design of therapeutic compounds selectively targeting the SCFA receptors.

Modelling and fixed bed column adsorption of Cr(VI) onto orthophosphoric acid-activated lignin

The advantage of using an available and abundant residual biomass, such as lignin, as a raw material for activated carbons is that it provides additional economical interest to the technical studies. In the current investigation, a more complete understanding of adsorption of Cr(VI) from aqueous systems onto H PO -acid activated lignin has been achieved via microcolumns, which were operated under various process conditions. The practice of using microcolumn is appropriate for defining the adsorption parameters and for screening a large number of potential adsorbents. The effects of solution pH (2-8), initial metal ion concentration (0.483-1.981 mmol·L ), flow rate (1.0-3.1 cm ·min ), ionic strength (0.01-0.30 mmol·L ) and adsorbent mass (0.11-0.465 g) on Cr(VI) adsorption were studied by assessing the microcolumn breakthrough curve. The microcolumn data were fitted by the Thomas model, the modified Dose model and the BDST model. As expected, the adsorption capacity increased with initial Cr(VI) concentration. High linear flow rates, pH values and ionic strength led to early breakthrough of Cr(VI). The model constants obtained in this study can be used for the design of pilot scale adsorption process. © 2012 Chemical Industry and Engineering Society of China (CIESC) and Chemical Industry Press (CIP).

Quantitative structure-toxicity relationships for chlorophenols to bioluminescent lux-marked bacteria using atom-based semi-empirical molecular-orbital descriptors

Literature data on the toxicity of chlorophenols for three luminescent bacteria (Vibrio fischeri, and the lux-marked Pseudomonas fluorescens 10586s pUCD607 and Burkholderia spp. RASC c2 (Tn4431)) have been analyzed in relation to a set of computed molecular physico-chemical properties. The quantitative structure-toxicity relationships of the compounds in each species showed marked differences when based upon semi-empirical molecular-orbital molecular and atom based properties. For mono-, di- and tri-chlorophenols multiple linear regression analysis of V. fischeri toxicity showed a good correlation with the solvent accessible surface area and the charge on the oxygen atom. This correlation successfully predicted the toxicity of the heavily chlorinated phenols, suggesting in V. fischeri only one overall mechanism is present for all chlorophenols. Good correlations were also found for RASC c2 with molecular properties, such as the surface area and the nucleophilic super-delocalizability of the oxygen. In contrast the best QSTR for P. fluorescens contained the 2nd order connectivity index and ELUMO suggesting a different, more reactive mechanism. Cross-species correlations were examined, and between V. fischeri and RASC c2 the inclusion of the minimum value of the nucleophilic susceptibility on the ring carbons produced good results. Poorer correlations were found with P. fluorescens highlighting the relative similarity of V. fischeri and RASC c2, in contrast to that of P. fluorescens.

Chiral supported ionic liquid phase (CSILP) catalysts for greener asymmetric hydrogenation processes

Chiral supported ionic liquid phase (CSILP) catalysts were prepared by physical adsorption (within highly porous carbons or mesoporous silica) of Ir, Ru and Rh complexes as IrCl(COD)-(S, S)-BDPP, [IrCl-(S)-BINAP](2), RuCl(p-cymene)[(S, S)-Ts-DPEN], RuOTf(p-cymene)[(S, S)-Ts-DPEN], [Rh(COD)(S, S)-DIPAMP][BF4], and [Rh(COD)(R, R)-Me-DuPHOS][BF4]. For the syntheses of CSILP catalysts [EMIM][NTf2], [BMIM][BF4] and [BMIM][PF6] ionic liquids were used. Comparative homogeneous and heterogeneous experiments were carried out using the asymmetric hydrogenation of double -C N- and -C C- bonds in trimethylindolenine, 2-methylquinoline and dimethylitaconate, respectively. The conversion and enantioselectivity was found to depend on the nature of the complex (metal and ligand), the immobilization method used, nature of the ionic liquid, nature of the support and the experimental conditions. (C) 2012 Elsevier B.V. All rights reserved.

Mutual Solubilities of Ammonium-Based Ionic Liquids with Water and with Water/Methanol Mixture

Over the last two decades, ionic liquids have gained importance as alternative solvents to conventional VOCs in the field of homogeneous catalysis. This success is not only due to their ability to dissolve a large amount of metal catalysts, but it is also due to their potential to enhance yields of enantiopure products. The art of preparation of a specific enantiomer is a highly desired one and searched for in pharmaceutical industry. This work presents a study on solubility in water and in water/methanol mixture of a set of ILs composed of the bis (trifluoromethylsulfonyl) imide anion and of the N-alkyl-triethyl-ammonium cation (abbrev. [NR,222][NTf2]) with the alkyl chain R ranging from 6 to 12 carbons. Mutual solubilities between ILs and water, as well as between ILs and methanol/water mixture were investigated in detail. These solubilities were measured using two well-known and accurate experimental techniques based on a volumetric and a cloud-point methods. Both methods enabled us to measure the Tx diagrams reflecting the mutual solubilities between water (or water/methanol) and selected ILs in the temperature range from 293.15 to 338.15 K. The data were fitted by using the modified Flory-Huggins equation proposed by de Sousa and Rebelo and compared also with the prediction carried out by the Cosmo-RS methodology

NO-loaded Zn2+-exchanged zeolite materials: A potential bifunctional anti-bacterial strategy

Nitric oxide (NO) is important for the regulation of a number of diverse biological processes, including vascular tone, neurotransmission, inflammatory cell responsiveness, defence against invading pathogens and wound healing. Transition metal exchanged zeolites are nanoporous materials with high-capacity storage properties for gases such as NO. The NO stores are liberated upon contact with aqueous environments, thereby making them ideal candidates for use in biological and clinical settings. Here, we demonstrate the NO release capacity and powerful bactericidal properties of a novel NO-storing Zn2+-exchanged zeolite material at a 50 wt.% composition in a polytetrafluoroethylene polymer. Further to our published data showing the anti-thrombotic effects of a similar NO-loaded zeolite, this study demonstrates the antibacterial properties of NO-releasing zeolites against clinically relevant strains of bacteria, namely Gram-negative Pseudomonas aeruginosa and Gram-positive methicillin-sensitive and methicillin-resistant Staphylococcus aureus and Clostridium difficile. Thus our study highlights the potential of NO-loaded zeolites as biocompatible medical device coatings with anti-infective properties. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Carbon nanotube modified carbon composite monoliths as superior adsorbents for carbon dioxide capture

Carbon composite monoliths were prepared from a commercial phenolic resin mixed with just 1 wt% of carbon nanotubes (CNTs) followed by carbonization and physical activation with CO. The products possess a hierarchical macroporous-microporous structure and superior CO adsorption properties. In particular, they show the top-ranked CO capacity (52 mg CO per g adsorbent at 25 °C and 114 mmHg) under low CO partial pressures, which is of more relevance for flue gas applications. This matches or exceeds those of carbons produced by complex chemical activation and functionalization. Our study demonstrates an effective way to create narrow micropores through structural modification of carbon composites by CNTs. © 2013 The Royal Society of Chemistry.

Hexavalent Chromium Adsorption by a Novel Activated Carbon Prepared by Microwave Activation

Microwave heating reduces the preparation time and improves the adsorption quality of activated carbon. In this study, activated carbon was prepared by impregnation of palm kernel fiber with phosphoric acid followed by microwave activation. Three different types of activated carbon were prepared, having high surface areas of 872 m2 g-1, 1256 m2 g-1, and 952 m2 g-1 and pore volumes of 0.598 cc g-1, 1.010 cc g-1, and 0.778 cc g-1, respectively. The combined effects of the different process parameters, such as the initial adsorbate concentration, pH, and temperature, on adsorption efficiency were explored with the help of Box-Behnken design for response surface methodology (RSM). The adsorption rate could be expressed by a polynomial equation as the function of the independent variables. The hexavalent chromium adsorption rate was found to be 19.1 mg g-1 at the optimized conditions of the process parameters, i.e., initial concentration of 60 mg L-1, pH of 3, and operating temperature of 50 oC. Adsorption of Cr(VI) by the prepared activated carbon was spontaneous and followed second-order kinetics. The adsorption mechanism can be described by the Freundlich Isotherm model. The prepared activated carbon has demonstrated comparable performance to other available activated carbons for the adsorption of Cr(VI).

Arsenic(III,V) adsorption onto charred dolomite: charring optimization and batch studies

In this work, the removal of arsenic from aqueous solutions onto thermally processed dolomite is investigated. The dolomite was thermally processed (charred) at temperatures of 600, 700 and 800 degrees C for 1, 2, 4 and 8 h. Isotherm experiments were carried out on these samples over a wide pH range. A complete arsenic removal was achieved over the pH range studied when using the 800 degrees C charred dolomite. However, at this temperature, thermal degradation of the dolomite weakens its structure due to the decomposition of the magnesium carbonate, leading to a partial dissolution. For this reason, the dolomitic sorbent chosen for further investigations was the 8 h at 700 degrees C material. Isotherm studies indicated that the Langmuir model was successful in describing the process to a better extent than the Freundlich model for the As(V) adsorption on the selected charred dolomite. However, for the As(III) adsorption, the Freundlich model was more successful in describing the process. The maximum adsorption capacities of charred dolomite for arsenite and arsenate ions are 1.846 and 2.157 mg/g, respectively. It was found that both the pseudo first- and second-order kinetic models are able to describe the experimental data (R-2 > 0.980). The data suggest the charring process allows dissociation of the dolomite to calcium carbonate and magnesium oxide, which accelerates the process of arsenic oxide and arsenic carbonate precipitation. (C) 2014 Elsevier B.V. All rights reserved.

Structure and Catalytic Activity of Gold in Low-Temperature CO Oxidation

Structures and catalytic activities of Au thin films supported at anatase TiO(2)(101)) and a Au substrate are studied by using density functional theory calculations. The results show that O(2) can hardly adsorb at flat and stepped Au thin films, even supported by fully reduced TiO(2)(101) that can highly disperse Au atoms and offer strong electronic promotion. Interestingly, in both oxide-supported and pure Au. systems, wire-structured Au can adsorb both CO and O(2) rather strongly, and kinetic analysis suggests its high catalytic activity for low-temperature CO oxidation. The d-band center of Au at the catalytic site is determined to account for the unusual activity of the wire-structured film. A generalized structural model based on the wire-structured film is proposed for active Au, and possible support effects are discussed: Selected oxide surfaces can disperse Au atoms and stabilize the formation of a filmlike structure; they may also serve as a template for the preferential arrangement of Au atoms in a wire structure under low Au coverage.

Quality Assurance for GCxGC-FID, Accreditation for TPH CWG Protocol

A new technological approach in the analysis and forensic interpretation of Total Hydrocarbons in soils and waters using 2D Gas Chromatography method (GC-GC) was developed alongside environmental forensic and the assessment models to provide better customer products for the environmental industry.
The objective was to develop an analytical methodology for TPH CWG. Raw data from this method is then to be evaluated for forensic interpretation and risk assessment modelling. Access will be made available to the expertise in methods of forensic tracing contaminant sources, transport modelling, human health risk modelling and detailed quantitative risk assessment.
The quantification of internal standards was key to the development of this method. As the laboratory does not test for TPH in 1D, it was requested during INAB ISO 17025 audit to individually map out where each compound falls chromatographically in the 2D. This was done through comparing carbon equivalent numbers to the n-alkane carbons. This proved e.g. 2-methylnaphthalene has 11 carbons in its structure; its carbon equivalent is 12.84 , the result of which falls within the band of Aromatic eC12-eC16 as opposed to expected eC10-eC12. This was carried out for all 16 PAH (polyaromatic hydrocarbons) and BTEX (benzene, toluene, ethylbenzene and o, m and p-xylenes). The n-alkanes were also assigned to their corresponding aliphatic bands e.g. nC8 would be expected to be in nC8-nC10.
The method was validated through a designated systematic experimental protocol and was challenged with spikes of known concentration of hydrocarbon parameters such as recoveries, precision, bias and linearity. The method was verified by testing a certified reference material which was used as a proficiency round of testing for numerous laboratories.
It is hoped that the method will be used in conjunction with the analysis through Bonn Agreement with their OSINet group. This is a panel of experts and laboratories (including CLS) who forensically identify oil spill contamination from a water source.
This method can prove itself to be a robust method and benefit the industry for contaminated land and water but the method needs to be seen as separate from the regular 1D chromatography. It will help identify contaminants and assist consultants, regulators, clients and scientists valuable information not seen in 1D