A variety of paired electrosyntheses of organic compounds are generally classified into some reaction types and are reviewed with illustrations for typical examples. The following previous and present studies made by the authors and co-workers are also introduced in detail from a practical aspect : that is, paired electmsyntheses of (a) gluconic acid and sorbitol from glucose, (b) methyl ethyl ketone from 2, 3-butanedio1, (c) sulfones, nitrones and aminoiminomethanesulfonic acids from sulfides, N-hydroxylamines and thioureas, respectively, (d) optically active alcohols from racemic ones (optical resolution) and (e) polysilanes from dichlorosilanes (sacrificial anode).
Electroless metal deposition plays an important role in the fabrication of printed circuit boards mainly due to its ability to produce uniform metal films on insulating substrates (e.g., ceramics, glass, polymers). However, the adhesion of the electrolessly deposited metal films, particularly coinage metals (Cu, Ag, Au) on ceramic substrates is usually poor, even on roughened substrates. Nevertherless, using our newly developed electroless metal deposition process, which is characterized by the use of a ZnO thin film as an intermediate layer between the substrate and the metal deposit, metal films with high adhesive strength can be achieved even on smooth glass substrates. In addition, this new process possesses the advantages of 1) simple processing procedures and 2) the ability to fabricate fine metal patterns in a fully additive fashion based on the photosensitivity of the ZnO films. New functions based on this process have been discovered in our recent research. In the present paper, the processing steps involved in this new method, the formation mechanism of catalytic Pd particles, the adhesion mechanism, as well as its possible applications in pattern fabrication, are briefly reviewed, based on our recent work.
The intracellular potentia1 (VICP) and the cell membrane electrical impedance (ZCM) of a cultured tobacco cel1, line BY-2, were measured simultaneously using a multifunctional microelectrode. In the experiment done in this study, VICP corresponded to the cross membrane potentia1 (VCMP) of the cell. When a control potentia1 (VCON) was varied stepwise in a range from −100 ~ +100mV, VCMP changed accordingly without any significant change in |ZCM|. The relationship between VCON and the change in VCMP (ΔVCMP) showed an asymmetrical property; ΔVCMP/VCON for positive VCON was smaller than that for negative VCON.
The electrolytic conductivity and charge-discharge characteristics of lithium electrodes were examined in three types of tetrahydrofurans (tetrahydrofuran, 2-methyl-tetrahydrofuran and 2, 5-dimethyltetrahydrofuran)-3-propy1-4-methylsydnone (3-PMSD) binary solvent electrolytes. The order of decrease of the specific conductivities in the electrolytes except LiBPh4 is LiN (CF3SO2)2>LiPF6>LiC1O4>LiBF4>LiCF3SO3. The conductivity in the LiBPh4 electrolyte continued to gradually increase with the addition of the tetrahydrofurans. The energy density for a Li/V2O5 (2025) coin-type cell in LiN(CF3SO2)2/3-PMSD-tetrahydrofuran (THF) electrolyte at 0.9 mole fraction of THF was 380Wh kg−1, which is almost equal to that in an ethylene carbonate-1,2-dimethoxyethane equimolar solvent electrolyte containing LiPF6. The LiBPh4/3-PMSD-2-methyltetrahydrofuran (2-MeTHF) equimolar solvent electfolyte showed a moderate cycling efficiency of more than 60% at a higher cycle number. The dendrite formation observed in the LiBPh4 electrolyte using atomic force microscopy (AFM) was minimal in spite of the increased cycle number. In addition, the film in the LiBPh4 electrolyte seems to be very thin, that is, the film thickness on the Ni electrode affects the charge-discharge Process.
The electrocatalytic activity of Zn metal electrode for potentiostatic electroreduction of CO2 has been studied in aqueous solutions of several potassium salts. The reduction products are CO and formate of which faradaic efficiency for formation depend on both the supporting electrolyte and electrode potential. Zn electrode dissolved before the electrolysis in the electrolyte solutions at the rate of 0.85μmol cm−2h−1 in 0.05mol dm−3K2SO4 which is 3.5 times greater than that in 0.1mol dm−3KHCO3 solution. For CO formation, the partial current density is proportional to the CO2 partial pressure and almost independent of pH, the Tafel slope of current-potential curve is ca. 200mV/decade, and reaction orders are ca. 1and 0.5 about CO2 and Zn2+ ion, respectively, in all the potassium salt solutions. On the other hand, in the case of HCOO− formation, the partial current density did not depend on the Zn2+ concentration in the electrolytes.
A method to calculate charge and discharge curves of an electrochemical cell from the impedance data is described, and its validity is examined by measuring an impedance together with charge and discharge curves of a lithium cell with a high-area carbon electrode. The capacity to store and deliver electricity and the polarization voltage were well illustrated from the impedance spectroscopic data via a computational transformation. Since a method is a reversible conversion from a frequency domain to a time domain by the Fourier transform, impedance spectroscopic data are also obtained from the steady-state charge and discharge curves. A significance of introducing this complemental method to impedance measurements of the electrochemical cells especially in frequencies fromμHz to l Hz is described.
In situ quartz crystal microbalance (QCM) analysis indicated an anomalous behavior, namely a mass increase, during the dissolution (discharge) process of lithium in a LiPF6/propylene carbonate (PC) solution. Such behavior is unexpected in the dissolution of lithium and is only observed particularly in the LiPF6/PC system. The authors identified this phenomenon as ``healing process’’ of the surface film on lithium metal and further investigated. From resonance frequency shift (Δf) and resistance parameter (ΔR), in the real time and the in situ QCM measurements, semi-quantitative analysis was made on the behavior with respect to the mass and roughness changes of the surface film produced continuously on the lithium metal With an increase in discharge current density (ranging from 0.05 to 2.50mA cm−2), the mass increase became pronounced. The healing process is induced initially by the release of lithium ions whereby forms the pores of lithium in which lithium metal is partially exposed or most of the cases already covered with Li2CO3, LiOH, Li2O. The surface readily transformed to LiF by the reaction of them with HF (formed by the reaction of PF6− and a trace of H2O) which lead to a mass gain.
Conducting polymers based on polyanilines with highly soluble and yet sustain relatively high conductivity were attempted to synthesize by either electrochemical or chemical oxidation from the solutions containing aniline monomers and traces of para-substituted anilines, namely p-toluidine or sulfanilic acid. The resulting polymers turned out to have low molecular weight electroactive polyanilines terminated by them in the polymerization process. The as-grown polymers which are at the doped state, show high solubility (250mg m1−1) in N-methylpyrrolidinone, while ordinary polyanilines particularly at the doped state scarcely soluble in NMP or any other solvents. Gel permeation chromatography indicated that the number average molecular weight of such polymers were obtained as 4,500 to 6,100 (vs. polystyrene standards) which should be the lowest among the relevant data so far reported. The conductivity of these polymers were found unexptedly high（10−1 to 10−3 S cm−1） for other soluble polyanilines substituted with various functional groups（normally 10−5 to 10−7S cm−1). By casting these polymers from the NMP solutions at concentrations of max. 250mg m1−1, the thin and uniform polymer films (typically 0.1mm in thickness) were successfully formed on an anodized A1(Al2O3) foil to device Al electrolytic capacitors for further testing. The Al electrolytic capacitor displayed good/fair impedance-frequency characteristics in that they have relatively high resonance frequencies（in the order of 107Hz） and showed low equivalent series resistance (min. 1. 4Ω).
The coloring-bleaching process of the electrochromic device (ECD) with solid electrolyte has been studied by using microbalance and quadrupole mass spectrometer. ECD adsorbs H2O gas and releases O2 during coloring. The weight of ECD increases by the adsorbing H2O gas. During bleaching ECD releases H2 and H2O gases and the weight of ECD returns to the weight before coloring. The weight variation of ECD is proportional to the optical density. It is suggested that the adsorbing-releasing gases change the morphology of ECD membranes and cause the crystallization of the membranes and the deterioration of the electrode of ECD.
The MnO2/Li cylindrical cell has been developed using a lithium-aluminum alloy negative electrode and an electrolytic manganese dioxide positive electrode with high specific surface area. The cell capacity at −20°C with the lithium-aluminum negative electrode has retained 90% after stored for 40 days at 60°C. The high retention was explained by no formation of LiOH on the lithium-aluminum alloy surface in storage, though the formation of LiOH was observed in the pure lithium negative electrode. The cell voltage on pulse discharge at −20°C was improved by using the electrolytic manganese dioxide with high specific surface area, and the cell capacity at −20°C increased about 38% compared with the conventional electrolytic manganese dioxide.
Conductivities of basic AICl3-NaCI melts containing different oxidation states of selenium species have been measured. The dependencies of the conductivity on the mole fraction and oxidation states of selenium species are discussed. The melt containing only SeCl4 shows the linear relation between the conductivity and temperature. A maximum conductivity is obtained as the formal oxidation state of selenium is around 2.
Red (ca. 1.82eV) photoluminescence (PL) of porous silicon was quenched reversibly in accordance with adsorption and desorption of alcoholic OH groups. The alcoholic OH groups adsorbed on SiHx of porous silicon with hydrogen bonding. From plots of log (PL100−PLT)/PL100 vs. 1/T, where PL100 and PLT are the PL intensities at 100 and TK, respectively, the activation energy of ca. 50eV was calculated for the non-radiative deactivation path of the excited electrons which are in an energy state possible to emit red PL. For the nonradiative deactivation path that were made with the adsorption of alcoholic OH groups, the activation energy was assumed to be negligible and independent on temperature.
LiCo0.5Ni0.5O2, LiAl0.25Ni0.75O2 and Li4Mn5O12 films were prepared by electrostatic spray deposition (ESD) onto gold substrates, and thelr stabilities in (62+38) mol% (Li+K) CO3 at 923K under an oxidant gas condition were investigated by XRD and EDX techniques. XRD measurements revealed that after immersion in the melt, the LiCo0.5Ni0.5O2 maintained the hexagonal structure, while the cubic phase of Li4Mn5O12 changed to a monoclinic of Li2MnO3. The XRD pattern of LiAl0.25Ni0.75O2 showed low crystallinity. The atomic ratios of Co/Ni and Al/Ni in the Ni-containing oxide films were found to be increased after immersion in the melt by EDX analysis, indicating that the nickel partly dissolved into the melt. The oxygen reduction currents at all the films were observed by cyclic voltammetry. It showed that the use of manganese is also hopeful as a cathode material of MCFC.