Sulfonated microporous polymer membranes with fast and selective ion transport for electrochemical energy conversion and storage

Membranes with fast and selective transport of protons and cations are required for a wide range of electrochemical energy conversion and storage devices, such as proton-exchange membrane (PEM) fuel cells and redox flow batteries. Here we report a new approach to designing solution-processable ion-selective polymer membranes with both intrinsic microporosity and ion-conductive functionality. This was achieved by synthesizing polymers with rigid and contorted backbones, which incorporate hydrophobic fluorinated and hydrophilic sulfonic acid functional groups, to produce membranes with negatively-charged subnanometer-sized confined ionic channels. The facilitated transport of protons and cations through these membranes, as well as high selectivity towards nanometer-sized redox-active molecules, enable efficient and stable operation of an aqueous alkaline quinone redox flow battery and a hydrogen PEM fuel cell. This membrane design strategy paves the way for producing a new-generation of ion-exchange membranes for electrochemical energy conversion and storage applications

Flow Batteries: Alkaline Benzoquinone Aqueous Flow Battery for Large-Scale Storage of Electrical Energy

We introduce an aqueous flow battery based on low-cost, non-flammable, non-corrosive and Earth-abundant elements. During charging, electrons are stored in a concentrated water solution of 2,5-dihydroxy-1,4-benzoquinone (DHBQ), which rapidly receives electrons with inexpensive carbon electrodes without the assistance of any metal electro-catalyst. Electrons are withdrawn from a second water solution of a food additive, potassium ferrocyanide (K4Fe(CN)6). When these two solutions flow along opposite sides of a cation-conducting membrane, this flow battery delivers a cell potential of 1.21 V, a peak galvanic power density of 300 mW/cm2 and a coulombic efficiency exceeding 99%. Continuous cell cycling at 100 mA/cm2 shows a capacity retention rate of 99.76%/cycle over 150 cycles. Various molecular modifications involving substitution for hydrogens on the aryl ring were implemented to block decomposition by nucleophilic attack of hydroxide ions in solution. These modifications resulted in increased capacity retention rates of up to 99.962%/cycle over 400 consecutive cycles, accompanied by changes in voltage, solubility, kinetics and cell resistance. Quantum chemistry calculations of a large number of organic compounds predicted a number of related structures that should have even higher performance and stability. Flow batteries based on alkaline-soluble dihydroxybenzoquinones and derivatives are promising candidates for large-scale, stationary-storage of electrical energy.Chemistry and Chemical BiologyEngineering and Applied Science

Highly Conductive and Water-Swelling Resistant Anion Exchange Membrane for Alkaline Fuel Cells

To ameliorate the trade-off effect between ionic conductivity and water swelling of anion exchange membranes (AEMs), a crosslinked, hyperbranched membrane (C-HBM) combining the advantages of densely functionalization architecture and crosslinking structure was fabricated by the quaternization of the hyperbranched poly(4-vinylbenzyl chloride) (HB-PVBC) with a multiamine oligomer poly(N,N-Dimethylbenzylamine). The membrane displayed well-developed microphase separation morphology, as confirmed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Moreover, the corresponding high ionic conductivity, strongly depressed water swelling, high thermal stability, and acceptable alkaline stability were achieved. Of special note is the much higher ratio of hydroxide conductivity to water swelling (33.0) than that of most published side-chain type, block, and densely functionalized AEMs, implying its higher potential for application in fuel cells

DEVELOPMENT AND VALIDATION OF A FAST SFC METHOD FOR THE ANALYSIS OF FLAVONOIDS IN PLANT EXTRACTS

Flavonoids from plants always show a wide range of biological activities [1-2]. In the present study, a rapid and highly efficient supercritical fluid chromatography (SFC) method was developed for the separation of 12 flavonoids. After careful optimization, the 12 flavonoids were baseline separated on a ZORBAX RX-SIL column using gradient elution. A 0.1% phosphoric acid solution in methanol was found to be the most suitable polar mobile phase component for the separation of flavonoids. From the viewpoint of retention and resolution, a backpressure of 200 bar and a temperature of 40 °C were shown to give the best results. Compared with a previously developed reverse phase liquid chromatography method, the SFC method could provide flavonoid separations that were about three times faster, while maintaining good peak shape and comparable peak efficiency. This SFC method was validated and applied to the analysis of five flavonoids (kaempferol, luteolin, quercetin, luteoloside, buddleoside) present in Chrysanthemum morifolium Ramat. from different cultivars (Chuju, Gongju, Hangju, Boju). The results indicated a good repeatability and sensitivity for the quantification of the five analytes with RSDs for overall precision lower than 3%. The limits of detection ranged from 0.73 to 2.34 μg/mL, while the limits of quantification were between 2.19 and 5.86 μg/mL. The method showed that SFC could be employed as a useful tool for the quality assessment of Traditional Chinese medicines (TCMs) containing flavonoids as active components

Simultaneous Determination of Free Amino Acid Content in Different Teas using Supercritical Fluid Chromatography Coupled with Single Quadrupole Mass Spectrometry

Tea (Camellia sinensis L.) is a complex mixture containing a wide range of biological activities and has been used as widely consumed beverages and natural medicine for over thousand years [1-2]. In this study, a novel method for high-performance liquid chromatography with mass spectrometry (SFC-MS) has been developed to simultaneously determine the contents of 11 free amino acids in different types of teas (pu-erh tea, green tea, black tea and oolong tea). The separation conditions for the selected amino acids were carefully optimized such as the column type, temperature and backpressure, the type of additive. The best compromise for tested analytes in terms of chromatographic performance was obtained when water (5%) and trifluoroacetate acid (0.4%) were added to the supercritical carbon dioxide/methanol mobile phase. Finally, the developed SFC-MS method was successfully applied to the analysis of the 11 amino acids present in the teas and fully validated as well. The results indicated a good linearity (r ≥0.995), precision (RSD≤ 2.99%), stability (RSD≤ 2.88%) and accuracy (91.95%~107.99%). The limits of detection ranged from 1.42 to 14.69 ng/mL, respectively, while the limits of quantification were between 4.53 and 47.0 ng/mL. The content of the amino acids in six different tea samples were also determined and presented some difference basing on the fermentation processes. The proposed SFC-MS method showed a great potential in further investigations to differentiate tea varietie

Determination of saccharides in honey using supercritical fluid chromatography coupled with single quadrupole mass spectrometry

The efficient separation and accurate determination of saccharides still remains a challenge due to the wide variety of possible isomers, high polarity, similar chemical composition and absence of chromophores [1]. Supercritical fluid chromatography (SFC) is an attractive separation method often showing higher resolution and shorter analysis time compared to traditional GC and HPLC [2]. Few papers have reported on the SFC analysis of saccharides using standard compounds [3-4]. The aim of this study was to develop an efficient and sensitive method for the determination of fructose, glucose and sucrose in honey samples using SFC-MS. The method validation and application to the determination of these saccharides in different honey samples were also performed

Supercritical Fluid Chromatography in Traditional Chinese Medicine Analysis

Traditional Chinese medicines (TCMs) are gaining increasing popularity throughout the world due to their long historical clinical practices. Highly efficient analytical separation tools are essential for investigating the mysterious properties of TCMs and their quality control. Supercritical fluid chromatography (SFC) showed a great potential in TCM analysis for both nonpolar and polar components. In this paper, an overview of the experimental conditions (i.e. detection mode, stationary phase, mobile phase composition, pressure and temperature) used in SFC for achiral separations of TCM components is presented and recent applications to the analysis of different classes of compounds extracted from TCMs, such as lipids, terpene and terpenoids, phenolic compounds, flavonoids, alkaloids, saponins and carbohydrates, will be briefly described