Keio University · Chemical Engineering
Professor Yasushi Katayama's research lab specializes in electrochemistry and materials science, focusing on the development and characterization of room-temperature ionic liquids (RTILs) for advanced electrochemical applications. Key research directions include the electrochemical behavior of oxygen and metal ions (e.g., Ag⁺, Co²⁺, Li⁺) in RTILs, the role of solvation structure and electric double layer in charge transfer kinetics, and the design of ionic liquid-based electrolytes for energy storage and electrodeposition. The lab also explores integrated electrochemical systems, such as micro DC-DC converters, by combining electrochemistry with microfabrication techniques.
Figures are computed from collected data and may differ slightly.
The electrochemical reduction of oxygen was investigated in some hydrophobic room-temperature molten salt systems (ionic liquids) consisting of bis(trifluoromethanesulfone)imide anion with trimethyl-n-hexylammonium 1-butyl-1-methylpyrrolidinium 1-ethyl-3-methylimidazolium or 1,2-dimethyl-3-propylimidazolium cation. The oxygen dissolved in these melts was reduced to the superoxide ion on a gold electrode. The superoxide ion was stable against the aliphatic and alicyclic organic cations and but re
The electrochemical behavior of oxygen /superoxide ion couple was investigated with the aid of the ultramicroelectrode technique in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI) room-temperature molten salt (ionic liquid). The diffusion coefficient of was at . The activation energy of the diffusion process of was estimated to be from the temperature dependence of the diffusion coefficient. The solubility of in BMPTFSI was at and decreased with an increase in temperatu
A room-temperature molten salt, 1-ethyl-3-methylimidazolium tetrafluoroborate with adequate purity was obtained simply by the reaction of 1-ethyl-3-methylimidazolium chloride and tetrafluoroboric acid. Silver tetrafluoroborate dissolves up to ∼0.2 mol dm−3 in at room temperature. Electrochemical deposition and dissolution of silver on a platinum electrode were found possible in containing The reduction of monovalent silver species is electrochemically irreversible, the rate constant being estima
In this paper, we report the newly developed DC-DC converter IC termed monolithic DC-DC converter, in which a thin-film inductor and power IC are integrated, and describe the micro DC-DC converter module utilizing this IC. The thin-film inductor used in the monolithic DC-DC converter was fabricated by RF sputtering, photosensitive polyimide lithography and electro-plating onto the power IC. The micro DC-DC converter module using the monolithic DC-DC converter achieved power density of 5.6 W/cm/s
The electrodeposition of cobalt was investigated in an ionic liquid, 1--butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide. The overpotential for the electrodeposition of Co was reduced remarkably by elevating the temperature up to , probably due to the change in the coordination environment of Co species. The addition of acetone led to the decrease in the overpotential, indicating the selective coordination of Co cation with acetone enhanced the charge transfer rate. It has been sugg
Electrochemical intercalation of lithium into graphite was investigated in trimethyl--hexylammonium bis(trifluoromethanesulfone)imide (TMHATFSI) room-temperature molten salt containing both lithium bis(trifluoromethanesulfone)imide (LiTFSI) and ethylene carbonate (EC). The electrochemical intercalation of the organic cations into graphite occurred in TMHATFSI molten salt regardless of the presence of LiTFSI. The addition of EC to TMHATFSI molten salt with LiTFSI resulted in the electrochemical f
Electrodeposition of metallic lithium has been investigated on a tungsten electrode in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfone)imide (BMPTFSI) room-temperature molten salt. It was suggested that a passivation film forms on the electrode surface as a result of the reductive decomposition of the organic cation, BMP+. The film obtained in the absence of LiTFSI seems to have no conductivity and reduced further at more negative potential. On the other hand, the film obtained in BMPT
The 3:1 compounds of and , precipitate from the eutectic melt containing trivalent rare earth species, RE(III), at 723 K. In the presence of O2−, and/or precipitate from the melt. In the case of Gd, the formation of and strongly depends on O2− ion concentration in the melt. Only precipitates selectively from the melt while precipitates selectively when . The relative stability of against , thermodynamically evaluated for the same melt condition, shows is preferentially formed for light earths wh
The electrochemical behavior of lead (Pb) was investigated in an amide-type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA), containing Pb(TFSA)2. The cathodic and anodic currents corresponding to electrodeposition and stripping of Pb, respectively, were observed by cyclic voltammetry. The formal potential of Pb(II)/Pb couple was found to be −0.68 V vs. Ag/Ag(I), which is more negative by 0.11 V than that of Sn(II)/Sn couple. The diffusion coefficient of P
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