Structural effects on the oxygen reduction reaction (ORR) have been studied on the low index planes of rutile TiO₂ doped with Nb (0.05–1 wt%) in 0.1 mol L⁻¹ HClO₄. The order of the ORR activity at 0.20 V (vs. RHE) is TiO₂(100) < TiO₂(111) < TiO₂(110), and the activity increases with increasing Nb concentration. The activity of TiO₂(110) is 5.6 times as high as that of TiO₂(100) at Nb concentration 1 wt%. The order of the ORR activity does not correlate with the amount of oxygen vacancy defects that are known as the active sites of the ORR of TiO₂ nanoparticles. The ORR activity of 1 wt%Nb-doped TiO₂(100) modified with melamine is 2.1 times higher than that of the unmodified one. The activity of 1 wt%Nb-doped TiO₂(110) modified with melamine is the highest in the low index planes of TiO₂. Modification by tetra–n–hexylammonium cation (THA⁺) affects the ORR activity slightly.

For the purpose of fabrication of novel all-solid-state supercapacitor systems, compatibility of a gel polymer electrolyte consisting of “water-in-salt” aqueous solutions of magnesium bis(trifluoromethane sulfonyl)imide in polyacrylamide matrix was compared with the lithium analogue via symmetric supercapacitor cells. Although the lithium gel electrolyte promotes an irreversible plateau at around 1.5 V during initial charging of a carbon nanofiber based cell, reversible charge–discharge can be up to 2.0 V for an activated carbon based cell. Magnesium gel electrolyte promotes charge–discharge at the first cycle. However, during subsequent cycles, the cells show severe capacitance degradation, probably because of Mg(OH)₂ precipitation at the negative electrode.

Demand for novel drug screening methods which are characterized by simple, rapid and low cost is increasing now. In this study, the simple and rapid evaluation of the anti-allergic effect of natural medicines on the degranulation of a model mast cell (RBL-2H3 cells) was successfully achieved by two-dimensional surface plasmon resonance (2D-SPR) measurement. The each cell response was observed by SPR imaging upon model antigen, Albumin from bovine serum, 2, 4-Dintrophenylated (DNP-BSA) stimulation after anti-DNP IgE sensitization on RBL-2H3 cells. Here glycyrrhizic acid (GA) and isoliquiritigenin (ISL) were examined as degranulation inhibitors. After the pretreatment with 30 µmol/L GA or 50 µmol/L ISL, the reflection intensity increase at cell regions upon DNP-BSA stimulation was completely suppressed. In addition, it was shown that the suppression of reflection intensity increase at cell regions in the 2D-SPR observation upon DNP-BSA stimulation was dependent on the GA and ISL concentration in pretreatment as well as β-hexosaminidase assay. These results demonstrated that the suppression effect of GA and ISL on the degranulation of RBL-2H3 cells could be evaluated by 2D-SPR observation at cell regions in quick and simple manner. Our study further suggested that 2D-SPR observation of mast cell response might be applicable to screen anti-allergic components of natural products and useful to discuss its inhibitory effect in the intracellular signaling pathway of mast cell upon antigen stimulation.

The electrochemical N(CF₃SO₂)₂⁻ (TFSA⁻) anion intercalation into graphite was studied, aiming at the use for Mg secondary batteries. In order to achieve both the Mg plating/stripping reaction and anion intercalation, the electrolyte solution consisting of Mg²⁺/glyme = 1 (mol) with hydrofluoroether (HFE) as the diluent was used. The Raman spectrum indicated that all glyme solvated Mg²⁺-ion, which led the improvement of anti-oxidation durability up to 4.5 V (vs. Mg²⁺/Mg). The TFSA⁻ anion intercalation took place in the solution with almost 100% of coulombic efficiency. Besides, the charge-discharge test exhibited the discharge plateau over 3.4 V (vs. Mg²⁺/Mg) with the capacity of ca. 70 mA h g⁻¹. The results indicated the anion intercalation into graphite will be the attractive candidate for Mg secondary batteries.

Degradation of LiMn₂O₄ in LiPF₆-based electrolyte solution is complicated due to the influence of PF₆⁻ anion. Decomposition of PF₆⁻ anion accelerates both of dissolution of manganese ion and surface-film formation. In this study, surface states of LiMn₂O₄ thin-film electrodes in LiPF₆/propylene carbonate (PC) derived from the surface-film formation were investigated using redox reaction of ferrocene and spectroscopic analyses. The spectroscopic analyses suggested that properties of the surface film depended the operation temperature (30 °C and 55 °C); a thinner surface film composed of LiF and PC decomposition products formed on LiMn₂O₄ at 30 °C and a thicker surface film was formed at 55 °C. The redox reaction of ferrocene clearly showed that LiMn₂O₄ was completely passivated at 30 °C, while it was partially passivated at 55 °C, indicating the surface film formed at 55 °C was not compact and LiMn₂O₄ was exposed to the electrolyte solution. It was one of the causes of the rapid degradation of LiMn₂O₄ at elevated temperatures in LiPF₆-based electrolyte solution.

Indigo is one of the oldest natural blue dyes. Microorganisms and their enzymatic activities are deeply involved in the traditional indigo staining procedure. To elucidate the mechanism of the microbial indigo reduction, we directly performed cyclic voltammetry on alkaline fermenting dye suspensions. A pair of characteristic redox peaks of leuco-indigo was observed in a supernatant fluid of the fermenting dye suspension. On the other hand, it was found that the indigo/leuco-indigo redox couple mediated two-way microbially catalyzed oxidation and reduction in a sediment-rich suspension of the fermenting suspension. Acetaldehyde was supposed to be the electron donor and acceptor of the catalytic reactions. In order to verify the bioelectrocatalytic reaction, we isolated indigo-reducing bacterium K2-3′ from the fermenting suspension, and the two-way bioelectrocatalysis was successfully restaged in a model system containing K2-3′ and methyl viologen (as a soluble mediator instead of indigo) as well as acetaldehyde at pH 10.

This study provides evidence of the enhancement of the oxygen reduction reaction (ORR) activity of Pt/C and Pd-core Pt-shell catalysts upon ionic liquid modification. Under high potential at 1.15 V (vs. reversible hydrogen electrode), the lower coverage of the oxide species on the Pt surface modified with [7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD)][bis(trifluoromethylsulfonyl)imide (NTf₂)] ionic liquid (IL) was confirmed by electrochemical analysis. Operando X-ray absorption spectra (XAS) of the ionic liquid-modified Pd-core Pt-shell catalyst displayed smaller 5d orbital vacancies than the naked catalyst. Shrinkage of Pt-Pt bond length was also displayed, indicating the suppression of oxidation. Thus, we conclude that the IL-modified systems are effective in avoiding the adsorption of oxide species on the Pt surface and improving the oxygen reduction activity.

In this study, we fabricated nitrogen-doped carbons (NDCs) derived from chitosan using a new synthesis method that combines the thermal decomposition of chitosan and chemical activation with ZnCl₂. Then, the effect of the activation temperature on the microstructure of NDCs was investigated. The performance of a gas diffusion-type oxygen electrode (GDE) using the obtained NDCs was evaluated using an oxygen reduction reaction in an alkaline solution. Finally, the relationship between the microstructure of NDCs and electrode performance was discussed. The surface area and total pore volume of the fabricated NDCs tended to increase with activation temperature, despite decreasing nitrogen content. Additionally, we found that the overpotential of GDE decreases with an increase in specific surface area and total pore volume. The microstructure of the NDCs was found to play a key role in improving the performance of GDEs. Furthermore, the GDE composed of fabricated NDCs with a high surface area and high pore volume exhibited a reduced activation overpotential than that of conventional Pt-loaded carbon black.

The simulation model of the direct electron transfer (DET)-type bioelectrocatalysis at a porous electrode indicates that the catalytic current is proportional to the real surface area (A), when A is small. When A is large, the catalytic current is saturated at a limited value controlled by the mass transfer in the porous structure. In this study, the bioelectrocatalytic currents at porous electrodes are analyzed based on their charging currents. Comparisons among the carbon composites constructed with Vulcan and exfoliated graphite (JSP) show that the interface between the Vulcan and JSP particles is more suitable for the DET-type bioelectrocatalysis of bilirubin oxidase (BOD) than that between the particles of the same type. In particular, the most suitable properties were achieved at a Vulcan : JSP ratio of 1 : 1 in the composite electrode. In these composites, the multipoint contact between the BOD molecule and electrode seems to result in a higher DET-type bioelectrocatalytic activity.

For the modification of reversibility of magnesium deposition–dissolution in non-aqueous glyme-based electrolytes, the surface of a magnesium metal or magnesium alloy AZ31 was covered by graphene oxide modified using Grignard reagent. After modification, the magnesium chloride moieties appeared to connect with oxygen-containing functional groups of graphene oxide. The magnesium electrode covered with MgCl-modified graphene oxide exhibited a reversible redox reaction assigned to the deposition–dissolution of magnesium from the substance without overpotential in a conventional magnesium salt – glyme solution. The MgCl-modified graphene oxide-covered magnesium alloy electrode was compatible with two-electrode test cells with Mo₆S₈ positive electrode.

Tin-plated copper tubes have been widely used in cold and hot water service systems. However, leakage accidents caused by pitting corrosion can occur in such tubes; therefore, it is necessary to evaluate the effects of major environmental factors on the occurrence of local corrosion to ultimately suppress this corrosion. In the present study, the anodic polarization curves of a tin-coated copper electrode were measured in simulated freshwater containing Cl⁻, SO₄²⁻, and HCO₃⁻. The anodic current increased suddenly and sharply due to the breakdown of the passive layer and the initiation and growth of pitting generation at the pitting potential. The pitting potential shifted to a more negative direction with increasing Cl⁻ and SO₄²⁻ concentrations. In contrast, the pitting potential shifted to more noble potentials upon increasing the HCO₃⁻ concentration, indicating that HCO₃⁻ has an inhibitory effect on pitting attack by Cl⁻ and SO₄²⁻. The quantitative relationship between each anion concentration and the pitting potential was determined by multiple regression analysis. A plot of the pitting potential predicted from the created regression equation and the measured values of the pitting potential showed a positive linear relationship.

The self-designed flow system was used to study the flow corrosion of X100 pipeline steel in simulated formation water environment by electrochemical measurements as well as computational fluid dynamics (CFD) simulation. The effects of fluid flow velocity and fluid impact angle on X100 steel were determined. When the fluid flow velocity changes between 0.5–2.0 m/s, X100 steel is controlled by activation, and as the flow velocity increases, the self-corrosion current I_corr increases, the corrosion rate increases; when the impact angle increases from 30° to 90°, the self-corrosion current I_corr decreases and the corrosion rate decreases. CFD simulations show that at different flow velocities and impact angles, the velocity field distribution on electrode surface is different. At the minimum impact angle of 30°, the electrode area has the largest flow velocity and shear stress, therefore the corrosion damage is the most serious.

In this report we present a straightforward and efficient electropolishing methodology of pure metallic titanium in two different electrolytic baths; choline chloride-ethanol (ChCl-eth.) and choline chloride-methanol-butanol (ChCl-meth.-but.) in molar ratios of 1 : 4 and 1 : 6 : 2, respectively at 20 °C. The electrolytic baths under study possess relatively low-cost and environmentally benign. In the electropolishing processes, potentiostatic technique was applied. For the surface characterizations both atomic force microscope (AFM) and scanning electron microscopy (SEM) were used. The results showed that titanium surface was polished electrochemically at nanoscale and relatively free from defects. The working voltages of 2 and 1.2 V were applied in ChCl-eth. and ChCl-meth.-but., respectively within a time scale of 40 minutes in the present electrolytic baths. The roughness of pure metallic titanium (ca. 120.5 nm) was reduced to 0.10 nm in ChCl-eth. and 0.66 nm in ChCl-meth.-but.

This report presents influence of water and copper salt on the anodic dissolution of metallic copper in a eutectic solvent of choline chloride and ethylene glycol (DES) in a 1 : 2 molar ratio. The mechanism of copper dissolution anodically was investigated using anodic linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Atomic force microscope (AFM) was used to examine the morphology and topography of the surface after electrochemical dissolution course. The addition of 1, 4, 8, 16 and 20 vol% of water cause pitting and has no significant impact on the electrochemical behavior, in particular the shape of anodic linear sweep voltammetry remains unchanged. The more profound effect was seen from the microscopic analysis. The addition of 0.1 and 0.81 M CuCl₂ into this eutectic solvent resulted in relatively high resistance at the interfacial region where charge transfer occurs during anodic dissolution of metallic copper using impedance responses. The results confirmed that water will not affect anodic dissolution behavior and the chemistry of dissolution in the deep eutectic solvent.