Showing papers on "Electrochemical window published in 2005"

Investigation of physicochemical properties of lactam-based Brønsted acidic ionic liquids.

Abstract: Novel lactam-cation-based Bronsted acid ionic liquids (ILs) were prepared through a simple and atom-economic neutralization reaction between a lactam, such as caprolactam and butyrolactam, and a Bronsted acid, HX, where X is BF4-, CF3COO-, phCOO-, ClCH2COO-, NO3-, or H2PO4-. The density, viscosity, acidic scale, electrochemical window, temperature dependency of ionic conductivity, and thermal property of these ILs were measured and investigated in detail. The results show that protonated caprolactam tetrafluoroborate (CPBF) has a relatively strong acidity with −0.22 of Hammett acidic scale H0 and caprolactam trifluoroacetate (CPTFA) and pyrrolidonium trifluoroacetate (PYTFA) ILs possess very low viscosities, that is, 28 cP and 11 cP, respectively. An investigation of thermal property showed that a wide liquid range (up to −90 °C), moderate thermal stability (up to 249 °C for 10% of decomposition), and complex polymorphism were observed in these ILs. In comparison to imidazolium-cation-based ILs, the lacta...

Electrochemical window of a LiCl-KCl-CsCl melt

Abstract: The electrochemical window of the LiCl-KCl-CsCl melt (57.5:13.3:29.2 mol %, m.p.; 538 K) was investigated at 573-723 K. The cathodic limit of this melt for a nickel electrode was confirmed as lithium deposition from the results of differential scanning calorimetry and inductively coupled plasma atomic emission spectroscopy. Conceming the anodic limit of this melt, chlorine was confirmed to be evolved on a glassy carbon electrode from the result of the gas analysis. The electrochemical windows were determined as 3.75 and 3.62 V at 573 and 723 K, respectively. These values agreed well with theoretical decomposition voltages of LiCl.

Interfacing Boron Doped Diamond and Biology: An Insight on Its Use for Bioanalytical Applications

Abstract: Boron doped diamond (BDD) films are promising materials for electroanalysis and bioelectroanalysis. This contribution gives a short review on BDD functionalization by chemical and biochemical entities and on the applications of BDD electrodes to electroanalysis of chemical compounds of biological interest. This review is illustrated by the developments on BDD interfaces in both these areas carried out in our group. BDD electrodes were prepared by means of microwave plasma-assisted CVD onto silicon substrate giving rise to H-terminated BDD films. Anodic polarization of BDD electrodes in aqueous media generates hydrophilic oxidized surfaces and extended electrochemical window in aqueous media. We took advantage of this enlarged electrochemical window together with the hydroxylated surface for the functionalization of BDD electrode surfaces with biomolecules and for bioelectroanalysis. We have designed a novel route of BDD functionalization using OH terminations of the anodized surface. The modification of the BDD surface with biotin groups will be presented here as biologically active model. Furthermore, as the anodic potential window of BDD increases upon electrochemical activation, 2′-deoxyguanosine (1.2 V vs. Ag/AgCl) and 2′-deoxyadenosine (1.5 V vs. Ag/AgCl) could be detected electrochemically with an acceptable signal to noise ratio. The electrochemical signature of each oxidizable base was assessed using differential pulse voltammetry (DPV). These experiments pointed towards adsorption of the oxidized products, which were investigated macroscopically by DPV and at the microscopic level by SECM (scanning electrochemical microscopy).

Application of Ionic Liquids to Double‐Layer Capacitors

Abstract: Ionic liquids have attracted much attention as liquid electrolytes for electrochemical energy storage devices to increase the device safety by taking advantages of their nonvolatile and nonflammable properties The double-layer capacitor (DLC) is an energy storage device, which accumulates electric charges at the interface between an electrode (electronic conductor) and an electrolyte (ionic conductor) The DLC based on a pair of activated carbon electrodes and a nonaqueous electrolyte solution is regarded as a promising candidate for the electrochemical energy storage device for hybrid electric vehicles and fuel cell electric vehicles, since it has higher pulse power capability than conventional rechargeable batteries The author reviews the technology of applying ionic liquids to DLCs as a liquid electrolyte based on the results in our laboratory [1-3] The DLC consisting of activated carbon cloth electrodes (SpectraCarb 2220 yarn) and an ionic liquid (EMI(CF3SO2)2N) was proposed by Covalent Associates, Inc in 1995 for the first time, which showed a moderate capacitance and poor cycleability at 3 V [4] Therefore, we have examined the performance of DLC composed of a pair of activated carbon electrodes (coconut shell charcoal, average pore diameter 20 nm, surface area 1700 mg, average particle size 10 μm) and an ionic liquid in comparison with a conventional nonaqueous electrolyte, 1 M Et3MeNBF4/PC (propylene carbonate), whose electrolytic conductivity is 135 mScm at 25C Several EMI salts were selected to test, since there is no ionic liquid except EMI (1-ethyl-3-methyimidazolium) and DMI (1,3-dimethylimidazolium) salts that has the electrolytic conductivity larger than 9 mScm at 25C with keeping the electrochemical window of EMI Figure 1 shows the change of the capacitances of 2032 coin-type DLCs using various ionic liquids, when operating temperature was varied from 25oC to -25oC The capacitances of ionic liquids at 25C were comparable to that of 1 M Et3MeNBF4/PC (105 Fg-charcoal), however, those of EMIBF4, EMITaF6, EMICF3SO3, and EMI(C2F5SO2)2N decreased rapidly with decreasing temperature

Progress in Characteristic and Application of Ionic Liquid as Green Solvent

Abstract: The ionic liquid keeps its liquid state at or near room temperature.As one of the most promising green solvents,the ionic liquid has characteristic of low melting point,low vapor pressure,wide electrochemical window,adjustable acidity,strong solubility and high viscosity and is widely used in separation,organic synthesis and catalytic reaction.Room temperature ionic liquid has attracted industrial interests because it is environmentally friendly catalysts as novel green solvents.

Room-temperature molten salts as new electrolytes

Abstract: Publisher Summary Salts such as sodium chloride need high temperatures to melt, although mixing these salts considerably lowers the melting points. However, some salts, mostly organic, are known to melt below room temperature. These salts are called room-temperature molten salts (RTMSs) or room-temperature ionic liquids. Nonvolatility makes their handling easier and prevents the electrolyte from drying up; nonflammability improves the safety of devices; and a wide electrochemical window raises power and energy densities. A wide liquid-phase temperature range enables the operation of the devices in various environments. RTMSs are applied as reaction solvents of organic syntheses and contain organic or inorganic fluoroanions as counteranions that are combined with some onium cations. In this chapter, syntheses and properties of RTMSs containing fluoroanions are described. Also, a brief introduction is given on their applications for electrochemical devices such as electric double-layer capacitors (EDLCs), fuel cells, lithium batteries, and dye-sensitized solar cells. The syntheses of room-temperature molten salts are discussed. Properties of room-temperature salts are detailed. Application of room-temperature molten salts to electrochemical devices is finally discussed.