Tsugumi Hayashi

Recovery of Poly Sulfide Anions in Basic Solution Produced by the Decomposition of H2S by Fullerene

To remove poly sulfide anions from basic solution, a fullerene/toluene solution was mixed with an aqueous solution containing S2 2- ions and agitated until the color of the aqueous phase changed from yellow to transparent. The treatment was repeated several times. During each treatment, white precipitates were produced in the aqueous phase and black crystals were formed after 4th treatment. XRD results indicated that former was elemental sulfur and the latter, fullerene-sulfur compounds. Thus, we succeed in extracting and separating poly sulfide ion from aqueous solution. By the fifth treatment, c.a. 675 S2 2- ions per one fullerene were successfully collected from the aqueous solution. This reaction can be applied to recovery of other anion species in basic solution.

Basic study for the construction of solar cell using CdS photocatalysts and Na2S4 electrolyte

Photoexcited electrons pathway from thin film consisting of semiconductor particles to electrode was tried to develop by using conducting polymers. PEDOT/PSS and polyaniline was selected as transparent conducting polymer material. In the case of the cell consisted by using polyaniline, it was confirmed that conductive emeraldine salt stated polyaniline converted to non-conductive emeraldine base state because of contact with strong basic Na2S4 electrolyte solution. On the other hand, as regards the cell with PEDOT/PSS, it was expected that positive and negative electrode short-circuited and/or Schottky junction was formed between CdS and PEDOT/PSS. The formation of Schottky junction between CdS and PEDOT/PSS was reduced the kinetic energy of the photoexcited electrons to 5.1eV which was the Fermi level of PEDOT. These electrons could not reduce Na2S4 electrolyte solution since oxidation-reduction potential was 4.1eV. As a result, it considered that photoexcited electrons transfer was restricted, which rea...

Effective hydrogen generation and resource circulation based on sulfur cycle system

For the effective hydrogen generation from H2S, it should be compatible that the increscent of the photocatalytic (or electrochemical) activities and the development of effective utilization method of by-products (poly sulfide ion). In this study, “system integration” to construct the sulfur cycle system, which is compatible with the increscent of the hydrogen and or electron energy generation ratio and resource circulation, is investigated. Photocatalytic hydrogen generation rate can be enhanced by using stratified photocatalysts. Photo excited electron can be transpired to electrode to convert the electron energy to hydrogen energy. Poly sulfide ion as the by-products can be transferred into elemental sulfur and/or industrial materials such as rubber. Moreover, elemental sulfur can be transferred into H2S which is the original materials for hydrogen generation. By using this “system integration”, the sulfur cycle system for the new energy generation can be constructed.

Effect of Metal Gradient In Nano Wall of Stratified Type Photocatalyst

Objective of study was the development of core-shell type ZnS-CdS photocatalyst with the stratified morphology. To form the stratified morphology, condition of the precursor is extremely important. For this purpose, three types of precursors, thus core-shell type, egg-shell type and uniform type, was tried to synthesize by utilizing the results of the calculation. The size of the synthesized precursor particles was about 40-100 nm. Main phase of the particle was gradually changed from ZnO (pH8.0) to Cd(OH)2 (pH9.5). Detailed analysis of the synthesized precursor was clearly demonstrated that these have the crystalline structure and each metal element was co-existed in one particle. Therefore, it could be concluded that core-shell type or uniform type precursor was successfully synthesized. Core-shell type ZnS-CdS stratified photocatalyst could be successfully synthesized by sulfurization for 1h, and it shows the high photocatalytic activity under visible light irradiation.