A novel surface modification approach using cold plasma treatment of carbon dioxide (CO2) was picked up to improve the capacitance and the energy storage performance of the electrode at higher current densities. The modified activated carbon (AC) electrodes for the electric double-layer capacitor were found to have greater capacitance than that of the untreated electrode at high charge/discharge current densities. The capacitance ratio was 2.0 at 100 mA/cm2. From N2 adsorption/desorption measurements and cycle performance, the effect of the surface modification of the activated carbon electrode was discussed on the basis of the physical and chemical properties of the surface.
Pt supported on a binary support of multi-walled carbon nanotube (CNT) and carbon black (CB) with different ratio of CNT and CB (Pt/CNT-CB) has been prepared by reducing H2PtCl6 with ethylene glycol. Pt/CNT-CB (CNT/CB=50/50, 80/20), Pt/CB and Pt/CNT have been used as electrocatalysts for cathode in polymer electrolyte fuel cells (PEFC). In the low current density region, the cathode with a CNT/CB ratio of 50/50 shows the best performance as compared to CNT based catalyst. Whereas in the high current density region, the cathode with a CNT/CB ratio of 80/20 exhibits the best performance.
CAT is a triazine moiety that has been used as one of the most popular herbicides, and is reported to be an endocrine disrupting chemical. To detect aqueous CAT specifically at low concentrations regulated regally, an electrochemical sensing system for CAT was developed by coupling a molecularly imprinted polymer for CAT (CAT-MIP) packed column and an electrochemical analyzer. We have already reported the preparation of CAT-MIP as an artificial sensor receptor. In order to establish the electrochemical sensing system of CAT, we fabricated an amalgamated gold electrode which was alloyed with mercury. The amalgamated gold electrode could detect the largest reductive current of CAT at pH 3.0 in 0.1 M KCl, up to 30 µM. The detection procedure of this sensing system is composed of a solid phase extraction with the CAT-MIP column and electrochemical determination of CAT in the eluent from the column. With the sensing system, CAT was detected specifically in aqueous samples by washing non-specific adsorption to the CAT-MIP column with dichloromethane. Fifteen nM of CAT, as legally regulated in Japan, was detected with the system.
Chlorobenzene was electrolyzed on polycrystalline platinum electrode in acetonitrile with various water concentrations at −3.02 V(vs. Fc/Fc+). Formation rate of the reduction products depend on water concentration remarkably. Benzene is a main product at [H2O]≤0.3 mol dm−3. At [H2O]≥0.35 mol dm−3, toluene is obtained as well as benzene. Partial current density of toluene gives maximum at [H2O]=0.44 mol dm−3. Formation of toluene closely relates with production of methane resulting from the decomposition of acetonitrile.
The relationship between electrical conductivity and dielectric relaxation was investigated for 20 atom % Nd doped CeO2 (Ce0.8Nd0.2O2−δ), which is a typical oxide-ion conductor. Computer simulation clarified that the anomaly large dielectric constant (εr′) originated from the superimposition of both Debye-type polarization and interfacial polarization between electrolyte and electrode. Two kinds of the Debye-type relaxation appeared equal and above 773 K, which were ascribed to defect associates, (NdCe′-VO••)• and (NdCe′-VO••-NdCe′)×. The frequency dependence of ac conductivity (σac) was successfully explained by analyzing the dielectric loss factor (εr″). The σac values in high temperature and high frequency regions agreed with dc conductivity (σdc). The activation energy for σdc agreed with that for high frequency Debye-type polarization.
Volatile Organic Compounds (VOCs), such as carbon tetrachloride(CCl4), tetra-chloro-ethlene (CCl2CCl2) and 1,2-dichloroetane (CH2ClCH2Cl), were decomposed by using molten alkaline hydroxide (NaOH) without any oxidizing gas such as air. Decomposition capability was evaluated with both decomposition efficiency of VOCs and concentrations of secondary compounds regenerated in a gas phase. It was found that these gases reacted remarkably with molten NaOH above 600°C and the decomposition efficiencies were above 99.9% by means of the gas chromatograph mass spectroscopy (GC-MS method). Thirteen kinds of organic chlorides in a gas phase were also measured, in accordance with JIS-K-0125 by GC-MS, to be found that each concentration was below the detective limit (0.05 vol.ppm). Methane and hydrogen were detected in exhaust gas as the other secondary regenerates, as were estimated with previous thermo-dynamical calculations by MALT-2. Based on these results, the authors estimated adequate chemical decomposition reactions.
Periodic electrochemical oscillation was observed in a certain potential region when electrodeposition of zinc was performed at the interface between n-butyl acetate and a ZnSO4 aqueous solution. It was found that the electrochemical oscillation takes place synchronously with the periodic motion of a meniscus formed on the perimeter of a working electrode at the interface. We concluded that the motion of the interface is associated with the change in the interfacial tension caused by consumption and restoration of zinc ions in the aqueous solution around the working electrode.
Room temperature ionic liquids based on tri-n-butylalkylphosphonium cations were physically and electrochemically characterized. Bis(trifluoromethylsulfonyl)imide-based phosphonium ionic liquids exhibited relatively low viscosities. Tri-n-butyloctylphosphonium cation gave low melting salts together with a wide variety of anions. Most phosphonium ionic liquids were thermally stable up to nearly 400°C. Linear sweep voltammetry showed that potential windows of bis(trifluoromethylsulfonyl)imide-based phosphonium ionic liquids were at least 5.7 V when a glassy carbon electrode was used. In cyclic voltammetric measurement, the redox response of Li in a phosphonium ionic liquid was observed.