2007 Fiscal Year Final Research Report Summary
Surfacede sign for highly efficient electrochemical detoxification of nitrate
| Project/Area Number |
17350075
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental chemistry
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| Research Institution | Hokkaido University |
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Principal Investigator |
SHIMAZU Katsuaki Hokkaido University, Faculty of Environmental Earth Science, Professor (30109417)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHINAGA Yusuke Tokyo Gakugei University, 自然化学系, Associate Professor (60322848)
NAKATA Kou Hokkaido University, Faculty of Environmental Earth Science, Assistant Professor (90250414)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Nitrate nitrogen / Detoxification / Tin-modified noble metal electrodes / Adsorbed nitrate ion / Adsorbed NO / Metal nanoparticles / Cyclodextrin monolayer / Nanostructured surface |
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| Research Abstract |
1. Reduction of nitrate and nitrite ions was conducted on five kinds of tin-modified noble metal electrodes. The metal-dependences of electrocatalytic activity and the accessibility of the electrode to the selective N_2 production, which was calculated based on ratios of numbers of cleaved N-O bonds, formed N-N and N-H bonds to those required for the production of N_2, were determined. These results provide the important guide in designing highly active and high N_2-selective electrocatalysts.
2. Structure and reactivity of the adsorbed species formed from nitrate and nitrite ions, and NO were examined infrared spectroscopy. The following new and useful information about the reaction mechanism was obtained. (1) The adsorbed species from nitrate was unidentate nitrate. (2) The reduction rate of linear NO was faster than that of bridged NO. (3) Tin atoms used as the modification of Pd electrodes enhanced the reduction rate of the adsorbed NO.
3. Sn-noble metal binary metal electrodes were prepared by the successive adsorption of Sn^<2+> ion and Pt- or Pd-complexes on polycrystalline gold electrodes. Although the loading of noble metal was less than 0.3 g cm^<-2> because it was determined by the adsorption amount of the complexes at a monolayer level, these electrodes showed very high catalytic activity for nitrate reduction. Therefore, it is proved that this new method for reducing the loading of noble metal on the electrode is useful.
4. Multilayers of Sn/Pd/Au and Sn/Pt nanoparticles were constructed on self-assembled monolayers. The three-dimensional extension of reaction sites up to 2-3 layers was clarified. In addition, we develop the novel method of preparing nanostructured surface using cyclodextrin as a molecular template. The reduction of molecular oxygen was also accelerated on the nanostructured surface constructed using an atomic template. These results show that it is important to prepare electrocatalysts with the structure controlled at a molecular level.
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