Ibuprofen (2-(p-isobutylphenyl)propionic acid) is adsorbed strongly onto the surface of commercial activated carbon and is never released thereafter by subsequent immersion in water. The electrochemical responses for the ibuprofen-adsorbed activated carbon electrode can be monitored via cyclic voltammetry and impedance spectrometry. The influence of adsorbed ibuprofen can be extracted. The adsorbed ibuprofen molecules passivate the pore surface of the activated carbon electrode and decrease its capacitance. The capacitance by ibuprofen adsorption remains decreased even after the exposure to a more positive potential.
Iron sulfide (FeSx) composite positive electrodes were prepared mechanochemistry and applied to all-solid-state lithium cells. The prepared composites, consisting of Fe, S, Li3PS4 solid electrolyte (SE), and vapor-growth carbon fiber (VGCF), were in amorphous state after ball milling for 10 h. An all-solid-state cell with an amorphous Fe-S-SE-VGCF composite as the positive electrode exhibits a high reversible capacity of 420 mAh per total weight of the composite electrode at a current density of 0.13 mA cm−2 at 25°C. The cell exhibited a capacity retention of 88% after 200 cycles at a current density of 0.64 mA cm−2 at 25°C. The all-solid-state cell using the Fe-S-SE-VGCF composite at a current density of 0.13 mA cm−2 at 100°C exhibited a higher reversible capacity of 550 mAh g−1. The Fe-S-SE-VGCF composite is thus a promising positive electrode material, with high capacity and good cycle performance for all-solid-state lithium secondary batteries.
Two types of the so-called “metal fog” were observed during Li electrodeposition in LiCl-KCl eutectic melt. One of them colored gray showed unique behaviors, and was hardly explained by the mechanisms reported before. In this study, the conditions to generate this “gray metal fog” have been investigated in detail, and its mechanism is discussed. A drop of the cathodic current and the subsequent current vibration were observed with the gray fog generation, and the in-situ observation indicated that a black film was formed on the surface of electrode just before this fog dispersion. The black film was formed only on an electrodeposited thin Li metal film, and spread from the edge of the electrode to the whole surface. The black film was formed and disappeared repeatedly, and the gray fog was seen only on the black film. These results suggest that the existence of the black film causes the gray fog generation, and that the film is formed electrochemically and decomposed spontaneously.
The characteristics for 3,4,9,10-perylenetetracarboxylic-bisbenzimidazole (PTCBI, an n-type semiconductor) and 29H,31H-phthalocyanine (H2Pc, a p-type semiconductor) as organic p/n bilayer and bulk heterojunction (BHJ) photoelectrodes were studied for the photooxidation of thiol. Based on the analysis in their absorption spectra, a new absorption band in the longer wavelength (λ > 800 nm) for both bilayer and co-deposited photoelectrode suggested a formation of charge transfer complex. A photoanodic current was observed at λ ∼ 880 nm for the both bilayer and co-deposited electrodes, while no absorption and photocurrent for single layers of PTCBI and H2Pc. By assuming the Langmuir adsorption equilibrium at the solid/water interface, the kinetic parameters for the photoanodic current of thiol was analyzed for the longer wavelength of irradiation (λ ∼ 900 nm), and it was indicated that the rate of oxidation in the co-deposited was higher than that of the bilayer due efficient charge separation in the charge transfer complex.
This paper reports unusual diffusion-controlled growth of TiO2 mesoporous anodic films on titanium in hot phosphate/glycerol electrolytes. The formation behavior was investigated by cyclic voltammetry (CV) between 0 and 5 V vs. Pt at 433 K. The current density became almost constant above 1.5 V vs. Pt during the positive potential sweep, and was maintained even during the negative potential sweep. This is contrast to a drastic decrease in current density in changing the direction of potential sweep from the positive to negative in fluoride-containing ethylene glycol electrolyte. The constant current density between 1.5 and 5 V vs. Pt increased with an increase in the basicity of the hot phosphate electrolyte, suggesting that the rate-determining step of the film formation in the hot phosphate electrolyte was diffusion process of oxygen sources in the electrolyte, not the ion migration in the thin barrier layer under the high electric field. When CV measurements were conducted to higher potentials up to 20 V vs. Pt, anatase was developed above 7 V vs. Pt, leading to generate oxygen gas. The film morphology was also potential-dependent and the diffusion current was also influenced by the film morphology as well as oxygen gas generation.
Electrodeposition of cadmium (Cd) was investigated in a hydrophobic room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) using CdCl2 as the source of Cd species in the presence of excess chloride ion. Raman spectroscopy and potentiometric measurement suggested formation of a cadmium tetrachlocomplex, [CdCl4]2−, in BMPCl/BMPTFSA. Cyclic voltammetry showed the possibility of electrochemical reduction from [CdCl4]2− to Cd(0) with interesting unusual electrochemical behavior, probably derived from the potential-dependent electric double layer structure typical to the ionic liquid. Electrodeposition of Cd was performed by potentiostatic electrolysis and the deposits were characterized by X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy.
To understand the role of water on zirconium passivation in n-butanol solutions containing Bun4NBr, composition and corrosion properties of the passive film were studied using cyclic voltammetry, X-ray photoelectron and electrochemical impedance spectroscopy. Zirconium undergoes spontaneous passivation followed by pitting corrosion as a result of passivity breakdown by the aggressive attack of bromide anions. The passive film consists mainly of ZrO2, ZrO2·2H2O and a small amount of zirconium butoxide. The pitting potential shifts positively and pitting corrosion is seriously inhibited with the addition of a small amount of water. Water improves the pitting corrosion resistance of the passive film by changing the thickness and the relative ratio of OH−/O2−. The result is helpful to electrosynthesize zirconium butoxide with high energy efficiency.
Structural effects on the activity for the oxygen reduction reaction (ORR) have been studied on single crystal electrodes of Pt modified with six aromatic organic molecules (AOMs). The AOMs examined affect the ORR activity slightly. However, the activity of the sites uncovered by AOMs increases after the modification: the ORR activity of uncovered Pt(111) area after the modification of phthalocyanine is 2.5 times as high as that of bare Pt(111). t-BuTAP and iron (II) phthalocyanine also enhance the ORR on Pt(997). These facts show that adsorbed AOMs can enhance the ORR activity of the uncovered active sites on Pt electrodes.