津田 哲哉

Investigating metal-ion transport in ionic liquid media is important to realize batteries and electrodeposition, which utilize intriguing properties of the media. An in situ electrochemical scanning electron microscopy together with X-ray fluorescence spectrometry is developed by a simple modification of an instrument as a tool for the investigation. Diffusion of silver ions (Ag+) in an ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonylamide (BMI-TFSA) is monitored as the time variation of Ag+ concentration during the anodic dissolution of a silver electrode. The results are analyzed by a digital simulation of the diffusion layer based on Fick's law. The diffusion coefficient of Ag+ is unexpectedly varied according to the concentration, and the tendency of variation is discussed in terms of viscosity change.

A composite of bithiazole-benzothiadiazole-based semiconducting conjugated copolymer and gold nano-particles (AuNP) was prepared in situ and characterized by transmission electron microscopy, therrnogravimetry, and UV-vis absorption spectroscopy. The polymer interacts with the nanoparticle surface through the nonbonding electrons of the nitrogen and sulfur atoms, which provides stability to the nanoparticles as well as planarity and rigidity to the polymer backbone. As a result, the effective conjugation length and delocalization of pi-electrons of the polymer improved as evident from 130 nm red-shift in the UV-vis absorption spectrum. The nanoparticle along with the chemisorbed layer of polymer acts as a template for the self-assembly of the remaining polymer which is dispersed in the solution through pi-pi-stacking and van der Waals interactions. The self-assembly process enhances the polymer packing as well as ordering as seen from the shorter d spacing and from the more than threefold increase in the intensity of X-ray diffraction of the composite film. The charge carrier mobilities in the short and long ranges were measured by flash-photolysis time-resolved microwave conductivity and space-charge-limited current methods, respectively, which showed enhancement for the composite material compared to the pristine polymer. A more significant increase was observed in the hole mobilities (more than 12-fold), and hence the p-type nature of the composite was further studied by preparing blend films with typical acceptors such as phenyl-C-61-butyric acid methyl ester (PCBM) and N,N'-bis(1-hexylheptyl)perylene-3,4-9,10-tetracarboxylbisimide (PBI). Due to its spherical geometry, PCBM was found to disturb the ordering of polymer chains in the composite, resulting in the lowering of photoconductivity signals. On the other hand planar PBI molecules coassemble with the composite leading to significant enhancement of photoconductivity. Thus, we demonstrated a versatile approach of controlling planarization, pi-stacking and ordering of a conjugated polymer leading to the improvement of optoelectronic properties using AuNPs as a template.

We report that the ionic-liquid gating of bulk single crystals of a topological insulator can control the type of the surface carriers and even results in ambipolar transport. This was made possible by the use of a highly bulk-insulating BiSbTeSe2 system where the chemical potential is located close to both the surface Dirac point and the middle of the bulk band gap. Thanks to the use of ionic liquid, the control of the surface chemical potential by gating was possible on the whole surface of a bulk three-dimensional sample, opening new experimental opportunities for topological insulators. In addition, our data suggest the existence of a nearly reversible electrochemical reaction that causes bulk carrier doping into the crystal during the ionic-liquid gating process.

Room temperature ionic liquid (RTIL) possessing negligible vapor pressure can be put in a vacuum chamber without vaporization. This fact enables to make wet condition even under vacuum condition although it is absolute common sense that vacuum conditions must be dry world. Based on this attracting fact, we have attempted to introduce RTILs to several kinds of instruments, which need to keep vacuum condition in their sample chamber for analyses and material productions. Introduction of RTIL to analyses requiring vacuum conditions including electron microscopy and energy dispersed X-ray fluorescence spectroscopy allows us to observe samples with wet condition and chemical reactions and to analyze these samples. Metal sputtering and quantum beam instruments are exploitable for production of metal nanoparticles. The resulting metal nanoparticles are quite stable and they keep their electrocatalytic activities. (C) The Electrochemical Society of Japan, All rights reserved.

Room-temperature ionic liquid (RTIL) that is a liquid salt at or below room temperature is expected to be an innovative functional solvent and a liquid material due to its anomalous physicochemical properties such as negligible vapor pressure, flame resistance, and relatively-high conductivity. With an eye on what RTIL has negligible vapor pressure, we have created the analytical technique combined with RTIL and secondary electron microscope (SEM). In this paper, we report several RTIL-based SEM techniques that will be a useful analytical method in both electrochemistry and life science. The aim of this study is to show the utility of the RTIL-based SEM techniques. (C) The Electrochemical Society of Japan, All rights reserved.

The electrochemistry of binuclear tungsten salt, K-3[W2Cl9], was examined in the Lewis acidic 66.7-33.3 mole percent (m/o) aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-[EtMeIm] Cl) room-temperature ionic liquid as it pertains to the electrodeposition of the Al-W alloy. We revealed that Al-W alloy without chloride contamination can be electrodeposited from the 66.7 m/o AlCl3-[EtMeIm]Cl with the K-3[W2Cl9]. Interestingly Al-W alloy having an amorphous phase as well as W-rich Al alloy over 96 atomic present (a/o) W were successfully produced. However the Al-W alloy became covered with powdery deposits with increasing the W content in the alloy. The resulting Al-W alloy showed a favorable chloride-induced pitting potential comparable to that produced by a usual sputtering method if the W content was less than ca. 3 a/o W.

Various metal nanoparticles including base metal were produced by a brief accelerated electron beam irradiation of 1-alkyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl) amide room-temperature ionic liquid without a stabilizing agent, which is usually employed so as to prevent aggregation.

Au nanoparticles that are expected to be a key material for supporting future technologies were produced with brief accelerated electron beam irradiation to various 1-alkyl-3-methylimidazolium cation ([R(1)MeIm](+))-based room-temperature ionic liquids (RTILs) with aurate. The resulting Au nanoparticles were able to remain in a nearly-monodispersed state in the RTILs for several weeks at least although the surface was not covered with a stabilizing agent, which is usually employed so as to prevent aggregation behaviour. The particle size increased with increasing the irradiation dose as well as decreasing the alkyl chain length of the [R(1)MeIm](+) if the RTIL consisted of the same anion species. The shapes of the Au nanoparticles obviously altered with the anionic species in the RTILs used for the preparation.

Establishment of a facile Pt nanoparticle-SWCNT composite fabrication method that never requires a laborious pretreatment of SWCNTs or any chemical reagent was achieved by using Pt-sputtered RTILs.

Au nano-particles were synthesized via a reductive reaction in ionic liquid solution containing Au(3+) ions using a low-energy electron irradiation technique. In this study, we focused on how the electron beam conditions (acceleration energy, beam current and irradiation time) and the kinds of ionic liquid affected the size and shape of the prepared Au particles. The sizes of the primary particles increased with higher acceleration energy of the electron beam, whereas they did not depend so much on the beam current. Although the amount of secondary particles increased with longer irradiation time, the sizes of the primary particles remained constant. The anion of the ionic liquid strongly affected the size and shape of the primary particles, which was due to the different local structure of the ionic liquid around the Au particles. When the thickness of the ionic liquid layer was smaller than the penetration length of the electron beam, the formation of secondary particles was suppressed. The present results gave an important knowledge for controlling the size and shape of the metal particles, which is important for application of various catalyst or devices.

A characteristic of negligible vapor pressure that a room temperature ionic liquid (RTIL) possesses enables us to introduce RTILs in the apparatus requiring vacuum conditions for material production and analyses. This combination creates a path toward development of new techniques under vacuum conditions. As for material production especially metal nanoparticle synthesis, those are magnetron sputtering onto TRILs, plasma reduction in RTILs, physical vapor deposition onto RTILs, and electron beam and g-ray irradiation to RTILs. Interestingly the nanoparticles prepared in RTILs without any stabilizing agent do not aggregate in the RTILs. Also, we can introduce RTILs in analytical instruments requiring vacuum conditions such as X-ray photospectroscopy (XPS), matrix-assisted laser desorption/ionization mass spectroscopy (MALDI, MS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The fact that the RTIL is not charged under irradiation by quantum beams enables us to establish new analytical techniques. Furthermore, homogeneous conditions that are obtainable by dissolving a substance in a RTIL are quite useful for conducting analyses using the instruments described above for example MALDI-MS with high reproducibility.

Pt nanoparticles can be produced by a Pt sputtering method onto trimethyl-n-propylammonium bis((trifluoromethyl)sulfonyl)amide (Me3PrNTf2N) room-temperature ionic liquid (RTIL) without stabilizing agents. Pt nanoparticles obtained by the Pt sputtering method showed mean particle size of ca. 2.3-2.4 nm independently of sputtering time. A Pt-embedded glassy carbon electrode (Pt-GCE) consisting of the Pt-sputtered RTIL and a glassy carbon plate showed a favorable catalytic activity to oxygen reduction reaction. The catalytic ability was enhanced by Me3PrNTf2N modification of the Pt-GCE. In addition. carbon monoxide never absorbed onto the RTIL-modified Pt-GCE. (C) 2009 Elsevier B.V. All rights reserved.

Palladium acetate was noncovalently immobilized as a supported ionic liquid catalyst (SILC) in a nanosilica dendrimer, PAMDMAM, with the aid of an ionic liquid to form a cluster catalyst of palladium nanoparticles. The pseudo-homogeneous heterogenized catalyst, Pd-nanoPAMDMAM-SILC, was effective for Suzuki-Miyaura reactions of ortho-substituted aryl bromides or aryl triflates without a ligand in 50% aqueous ethanol in air at room temperature. The catalyst could be re-used up to five times in 93% average yield after simple centrifugation. TON reached 176,000.

The electrodeposition of ternary Al-Mo-Ti alloy was examined in the Lewis acidic 66.7-33.3 percent mole fraction aluminum chloride–1-ethyl-3-methylimidazolium chloride (AlCl₃–EtMeImCl) room-temperature ionic liquid containing both (Mo₆Cl₈)Cl₄ and TiCl₂. All of the electrodeposited Al-Mo-Ti alloys were dense and compact, and they adhered well to the copper substrate. In simulated body fluid, e.g., Ringer's solution, the Al-Mo-Ti alloy showed better corrosion resistance than pure nickel although it was somewhat inferior to 316 L stainless steel that is one of typical metallic biomaterials. Open circuit experiments in Ringer's solution suggested that amorphous Al-Mo alloy is superior to Al-Ti and Al-Mo-Ti alloys as a metallic biomaterial because of the formation of more stable passivation layer.

Ionic liquids (ILs) including ambient-temperature molten salts, which exist in the liquid state even at room temperature, have a long research history. However, their applications were once limited because ILs were considered as highly moisture-sensitive solvents that should be handled in a glove box. After the first synthesis of moisture-stable ILs in 1992, their unique physicochemical properties became known in all scientific fields. ILs are composed solely of ions and exhibit several specific liquid-like properties, e.g., some ILs enable dissolution of insoluble bio-related materials and the use as tailor-made lubricants in industrial applications under extreme physicochemical conditions. Hybridization of us and other materials provides quasi-solid materials, which can be used to fabricate highly functional devices. ILs are also used as reaction media for electrochemical and chemical synthesis of nanomaterials. In addition, the negligible vapor pressure of ILs allows the fabrication of electrochemical devices that are operated under ambient conditions, and many liquid-vacuum technologies, such as X-ray photoelectron spectroscopy (XPS) analysis of liquids, electron microscopy of liquids, and sputtering and physical vapor deposition onto liquids. In this article, we review recent studies on ILs that are employed as functional advanced materials, advanced mediums for materials production, and components for preparing highly functional materials.

A simple and robust method to prepare nanciparticle-dispersed liquid crystals is demonstrated. Highly dispersed gold nanoparticle-liquid crystal suspensions are fabricated by simply sputter doping the gold target on the host liquid crystal (see figure). The existence of the nanoparticles is supported by optical extinction measurements, polarization optical microscopy, and transmission electron microscopy. An improvement in the electro-optic response, namely, a decrease in the threshold voltage, is also demonstrated in twist nematic devices fabricated using the nanoparticle-dispersed liquid crystal.

We have developed a system enabling in situ electron microscope observation of electrochemical reactions using room-temperature ionic liquid (RTIL). In this study the in situ electrochemical scanning electron microscopy (ECSEM) was employed to know information of metal ions dissolved in RTIL. An energy dispersive X-ray fluorescence spectrometer (EDX) allowed quantitative detection of Ag+ dissolved in RTIL with the concentration range from 0.002 to 2 mol dm(-3). When line and fixed-place EDX analysis was conducted at vicinity of an Ag electrode that was electrochemically oxidized in RTIL, concentration profile and time course concentration changes of Ag+ were able to be easily observed.

The Pt nanoparticles were prepared by direct Pt sputtering onto trimethyl-n-propylammonium bis((trifluoromethyl)sulfonyl)amide (Me3PrNTf2N) room-temperature ionic liquid (RTIL) without a stabilizing agent. The mean particle size (2.3 +/- 0.1 nm) was maintained substantially constant independently of the sputtering time if the sputtering time was less than 1800 sec. The obtained Pt nanoparticles were well-dispersed in the RTIL and could be immobilized on a single-walled carbon nanotube (SWCNT) by a simple process that was established in this research. The Pt-SWCNT composite material showed a remarkable catalytic activity to electrochemical oxygen reduction reaction more than a commercially available Pt nanoparticle-carbon composite catalyst. It suggests that the Pt-SWCNT composite material is one of the promising electrode catalysts for a PEM fuel cell system.

The specific conductivity of a polymer-room-temperature ionic liquid (RTIL) composite composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and 1-butyl-3-methylimidazolium bis((trifluoromethyl) sulfonyl) amide (BuMeImTf(2)N) was less than neat RTIL because of an increase in activation energy estimated from Arrhenius plot, which implies that there is an unignorable interaction between the polymer matrix and the RTIL. Electrochemical reactions in the PVdF-HFP-BuMeImTf(2)N composite with negligible vapor pressure were investigated by the use of in situ electrochemical scanning electron microscope (ECSEM) system. Those reactions include Ag electrodeposition and actuation behavior. The results suggested that in situ ECSEM technique has the great possibility to be a future electroanalytical chemical method.

Metal nanoparticles were prepared with gamma-ray and accelerator electron beam irradiation in the 1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (BuMeIm(+)Tf(2)N(-)) room-temperature ionic liquids. As for Au nanoparticles yielded in this investigation, the gamma-ray irradiation made the particle size smaller compared to that by the accelerator electron beam irradiation. It is interesting to note that the nanoparticles prepared in this article were very stable although the surface was not covered with a stabilizing agent, which is usually employed so as to prevent aggregation. Similarly, other metal nanoparticle productions such as Ag, Cu, Mg, Al, Zn, and Fe were also investigated by means of the accelerator electron beam irradiation. In addition, some RTILs with Au nanoparticles yielded by the irradiation experiment showed fluorescent behavior under ultraviolet irradiation of 365 nm. It implies that the RTILs contain Au nanoparticles as well as Au clusters that cannot be observed by a common TEM system. In this study, we also found that the Si wafer, on which NaAuCl4 center dot 2H(2)O-added RTIL was spread, has distinctive two-dimensional Au microstructure crystals on the surface after the accelerator electron beam irradiation.

The electrochemistry of Cu(I) oxide (Cu(2)O) was examined in the 66.7-33.3% mole fraction (m/o) urea-choline chloride melt. Electrochemical parameters that were measured include the standard heterogeneous rate constant and transfer coefficient of the Cu(I)/Cu(II) reaction and the Cu(I) diffusion coefficient. Data about the density, equivalent conductance, and absolute viscosity of this melt were obtained over the temperature range of 298-353 K. The conductivity and viscosity exhibited the non-Arrhenius behavior typical of glass-forming liquids. Overall, the physicochemical properties of the urea-choline chloride melt are comparable to those of common room-temperature ionic liquids. The electrodeposition of Cu was examined on glassy carbon and platinum electrodes by using potential-step techniques. The critical number of atoms required for the formation of a stable nucleus on glassy carbon was similar to 0, indicating that active sites on the electrode surface served as critical nuclei. Cu deposits on Ni substrates were dense, nodular, and compact. (C) 2010 The Electrochemical Society. [DOI:10.1149/1.3377117] All rights reserved.

The authors report the expansion of the temperature range of cholesteric blue phases by doping nanoparticles. When spherical gold nanoparticles with a mean diameter of 3.7 nm were doped in a blue phase-exhibiting multi-component liquid crystal mixture, the temperature range of the cholesteric blue phase increased from 0.5 to 5 degrees C, while the clearing temperature decreased by approximately 13 degrees C. We believe that the mechanism stabilizing the cholesteric blue phase is similar to that of polymer-stabilized cholesteric blue phases: the nanoparticles accumulate in the lattice disclinations, stabilizing the overall cholesteric blue structure. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/APEX.2.121501

Platinum (Pt) nanoparticles were synthesized with room-temperature ionic liquid (RTIL)-sputtering method under dry N-2 or Ar atmosphere. The resulting Pt nanoparticles were well-dispersed in trimethyl-n-propylammonium bis((trifluoromethyl)sulfonyl)amide RTIL without any additive like dispersant. Electrocatalytic activity of the Pt nanoparticles embedded on a glassy carbon electrode (GCE) toward oxygen reduction reaction was examined. It was then found that the catalytic activity increases with increment of heat temperature for embedding the Pt nanoparticles onto GCE if the nanoparticles are synthesized under Ar atmosphere.

Mass production of gold nanoparticles in room-temperature ionic liquids without any stabilizing agents has been achieved with radiation irradiation, i.e., accelerated electron beam and gamma-ray.

The anodic electrode behavior for a p-type silicon single crystal electrode ((10 0), p = 0.01-0.02 Q cm, boron doped) was examined in the 1-ethyl-3-methyl imidazolium fluorohydrogenate, EtMeIm(FH)(2.3)F, room-temperature ionic liquid (RTIL). The electrochemical behavior was very similar to that in conventional HF aqueous solution. After the anodic electrode reaction, the Si electrode was uniformly covered with a mesoporous Si layer having a pore size of similar to 25 nm. The mesoporous layer did not exhibit a photoluminescence spectrum in the visible region due to the lack of Si-H termination. However, after chemical treatment with an ethanolic HF solution, a subset of the porous Si samples showed a very weak photoluminescence. (c) 2007 Elsevier Ltd. All rights reserved.

The physicochemical properties of urea-salt based melts such as the 66.7-33.3 mol % mixture of urea and choline chloride are comparable to those of many room-temperature ionic liquids. Copper (I) oxide dissolves in this melt to form complex ions. The standard heterogeneous rate constants and transfer coefficients for the Cu(I)/Cu(II) and Cu(I)/Cu(0) electrode reactions were determined in this melt at both glassy carbon and platinum electrodes by using cyclic and rotating disk electrode voltammetric methods. The electrodeposition of copper was investigated on glassy carbon by using chronoamperometry. Comparison of the dimensionless data with the corresponding theoretical models for three-dimensional nucleation indicated that the copper nucleation process was intermediate between the limiting cases for instantaneous and progressive nucleation. This suggests that nucleation of copper on glassy carbon proceeded at a finite number of active sites. ©The Electrochemical Society.

The direct electrolytic reduction of solid SiO2 has been investigated in molten CaCl2 at 1123 K aiming at the production of solar grade Si (SOG-Si). The target impurity levels for Si in the present study were calculated from the acceptable impurity levels for SOG-Si and the segregation coefficients for the impurity elements. New types of SiO2 contacting electrodes, in which SiO2 directly contacts with only Si, were devised to reduce metal contaminations in the produced Si. By using the new SiO2 contacting electrodes and a quartz vessel, most of the metal impurities were significantly reduced to be below the target levels. When NH4OH/H2O2/H2O, HCl/H 2O2/H2O and HF/H2O 2/H2O were used as a cleaning solution, remaining CaCl2 and some metal impurities in the produced Si were removed effectively. A basket type electrode was also tested for the reduction of granular SiO2. ©The Electrochemical Society.

Because aluminum is a less-noble metal which has the standard electrode potential of -1.676 V vs normal hydrogen electrode, it is impossible to obtain the electrodeposition of aluminum from an aqueous solution. No one has reported an electroless plating method of aluminum. We succeeded in demonstrating the electroless plating of aluminum from a room-temperature ionic liquid (RTIL). It was found from measurements of inductively coupled plasma, X-ray diffraction, scanning electron microscopy (SEM), SEM-energy-dispersive X-ray analysis, and glow discharge optical emission spectroscopy that dense, smooth, and pure aluminum plating was obtained from the RTIL by the electroless plating method. Moreover, the reaction mechanism of the electroless plating of aluminum from the RTIL electrolyte was electrochemically analyzed. (c) 2007 The Electrochemical Society.

Urea-EtMeImCl mixtures have melting points from 333 to 363 K at 10-80 mol% urea, and, at temperatures > 343 K, these melts show the highest conductivity reported to date for urea-based binary melts.

The electrodeposition of Al-Mo-Ti ternary alloys was examined in the Lewis acidic 66.7-33.3% mole fraction aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-EtMeImCl) room-temperature ionic liquid containing (Mo6Cl8) Cl-4 and TiCl2. The Mo content in the alloys varied with the applied current density and the Mo(II)/Ti(II) concentration ratio. The content was small and constant at 0.6 +/- 0.2% atomic fraction (a/o) and was independent of the deposition conditions. All the electrodeposited Al-Mo-Ti alloys were dense and compact and adhered well to the copper substrate. The deposit surface morphology depended on the applied current density and the Mo content of the alloys, as reported previously for the amorphous binary Al-Mo alloys. However, no amorphous glass phase could be detected in the Al-Mo-Ti ternary alloy samples; this behavior may be related to the presence of Ti. In summary, the addition of a small amount of Ti ( similar to 1 a/o) to the binary Al- Mo alloys resulted in a ternary alloy with a substantially improved chloride-induced pitting corrosion resistance compared to the related Al- Mo alloy. (c) 2008 The Electrochemical Society.

The recent results are described on the developments of ionic liquid (IL) fluorohydrogenates with high ionic conductivities and wide electrochemical windows. Several cyclic ammonium cations have been found to be combined with fluorohydrogenate anions giving a vacuum stable ionic liquid fluorohydrogenates, Cat+[(FH)2 3F]-. N-ethyl-N-methylpyrrolidinium fluorohydrogenate, EMPyrro(FH)2 3F, and N-allylpyridinium fluorohydrogenate, APyrid(FH)2 3F, exhibit wide electrochemical windows compared to the other fluorohydrogenates. A fluorohydrogenate fuel cell (FHFC) using HF-deficient IL, 1-ethyl-3-methyl-imidazolium fluorohydrogenate, EMIm(FH)1 3F, as the electrolyte operates at 120°C without humidification. The maximum output power so far obtained in the preliminary cell test is 41 mWcm-2 (0.41 V and 100 mA cm-2) at 40°C without humidification. copyright The Electrochemical Society.

This communication reports the formation of porous silicon (PS) by application of a positive potential on n- type silicon without illumination. PS films were formed in 1-ethyl-3-methylimidazolium oligofluorohydrogenate [EtMeIm(FH)(2.3)F] room-temperature ionic liquid, and the surface morphology strongly depended on the time and the applied potential. The results indicate that EtMeIm (FH)(2.3)F could be a nonaqueous solvent equivalent to hydrofluoric acid, allowing the formation of pores under anodic polarization. (c) 2007 The Electrochemical Society.

The effects of residual water and oxygen on the electrochemical processing step for the recovery of Cs+ extracted into the hydrophobic ionic liquids, tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide (Bu3MeN+Tf2N-) or N-methyl-N-propylpiperidinium bis((trifluoromethyl)sulfonyl)imide (MePrPip(+)Tf(2)N(-)) containing the lipophilic ionophore, calix[4]arene-bis (t-octylbenzo-crown-6) from simulated aqueous tank waste was investigated in the presence of residual water and oxygen. The electrochemical reduction of ionophore-bound Cs+ at Hg electrodes is surprisingly tolerant of small amounts of water, but greatly affected by oxygen. However, sparging with dry N-2 lowers the residual water and oxygen content of the extraction solvent to the level where the reduction of Cs+ at Hg is possible. Thus, the entire treatment cycle for the removal of Cs+ from tank waste using a hydrophobic ionic liquid can be carried out in an open cell, provided that the cell is sparged with dry N-2. MePrPip(+)Tf(2)N(-) + BOBCalixC6 was found to be a better extraction solvent for Cs+ than Bu3MeN+Tf2N- + BOBCalixC6, but the former solvent was unstable toward metallic Cs and/or Cs(Hg)(x). (c) 2006 The Electrochemical Society.

The anodic hydrogen electrode reaction was examined,in the Lewis acidic 66.7-33.3 mole percent (m/o) aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-EtMeImCl) ionic liquid and the LiCl-buffered neutral AlCl3-EtMeImCl ionic liquid containing LiAlH4. Raman spectroscopy experiments revealed that the Al2Cl7- anion in the acidic ionic liquid is directly involved in the dissolution of the LiAlH4. Electrochemical hydrogen generation was verified by gas chromatography and XRD for Pd and Ti electrodes polarized in the ionic liquid. The hydrogen electrode reaction was irreversible, i.e., it followed an EirCir mechanism in the 66.7 m/o ionic liquid at 298 K However, it was quasireversible in the LiCl-buffered ionic liquid at 353 K. and appeared to follow an EqrCir mechanism.

The voltammetric characteristics of polycrystalline Au and W electrodes cleaned (thermal annealing at 1100 K) and characterized (Auger electron spectroscopy) in ultrahigh vacuum (UHV) have been examined in ultrapure AlCl3/1-ethyl-3-methylimidazolium chloride (EtMeImCl) melts in UHV. These experiments were performed using a custom-designed transfer system that allows for the all-Al electrochemical cell to be filled with EtMeImCl in an auxiliary UHV chamber and later transferred under UHV to the main UHV chamber that houses the Auger electron spectrometer. The results obtained for the underpotential (UPD) and bulk deposition of Al on An were found to be very similar to those reported in the literature for measurements carried out under 1 atm of an inert gas in a glovebox. For the far more reactive W surfaces, voltammetric features ascribed to the stripping of underpotential-deposited Al could be observed following a single scan from 1.0 V vs Al3+/Al to a potential negative enough for bulk deposition of Al to ensue. This behavior is unlike that reported in the literature for experiments performed in a glovebox, which required either extensive potential cycling in the Al bulk deposition and stripping region or excursions to potentials positive enough for chlorine evolution to ensue for Al UPD features to be clearly discerned. These observations open new prospects for fundamental electrochemical studies of well-characterized, highly reactive metals, including single crystals, in a variety of low vapor pressure ionic liquids.