2014 Fiscal Year Annual Research Report
| Project/Area Number |
14J00061
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| Research Institution | Hokkaido University |
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Principal Investigator |
李 俊燮 北海道大学, 総合化学院, 特別研究員(DC2)
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| Project Period (FY) |
2014-04-25 – 2016-03-31
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| Keywords | sulfide / microelectrode / electrochemistry / sulfidation |
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| Outline of Annual Research Achievements |
Development of a system for safe generation of sulfide ions and sulfidation of a silver surface was established by using the microelectrode technique in order to investigate sulfidation of the metal surface of silver. Both silver microelectrode sulfidation and silver sulfide reduction on the microelectrode were reversible in Na2S solution and corresponded to Ag2S formation and HS- generation, respectively. Cathodic polarization of Ag2S, which covered the silver microelectrode, in pH 8.4 boric-borate buffer solution successfully generated HS- above a glass or silver substrate. Generation of HS- ions was strongly dependent on diffusion of HS- ions from the microelectrode to the substrate surface and solution bulk. Concentration of HS- in the vicinity of the substrate was dependent on the distance from the microelectrode to the substrate. The silver substrate was locally sulfidated by HS- generated from the microelectrode. However, at potentials higher than 0.14 VRHE, local sulfidation of the silver substrate was independent of the substrate potential. It is thought that mass transport of HS- is dominant for sulfidation of the silver substrate. The substrate potential as well as diffusion of HS- influences sulfidation of the silver substrate. Sulfidation by using the Ag/Ag2S microelectrode is safe and effective to investigate the mechanism and kinetics of sulfidation not only on a silver surface but also on various metal surfaces.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In my study, I aimed to examine reaction mechanisms and kinetics of depassivation process of stainless steel based on microelectrochemistry of metal sulfides. In order to investigate the role of the metal sulfide which is the origin of pitting of stainless steel, the new corrosion experimental methods were developed that can limit to generate very small amount of sulfide ion by electrochemically controlled systems. Sulfide ion generation and their diffusion phenomena and its application on silver surface had investigated.
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| Strategy for Future Research Activity |
Local sulfide ion generation system is going to apply on surface of stainless steel and the passive behavior of stainless steel is planning to examine in the presence of HS- where it is generated from local sulfide ion generator in order to determine the role of HS- to the stability change of passive film.
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