2015 Fiscal Year Annual Research Report
ｇ－Ｃ３Ｎ４／半導体複合材料の構築と表界面制御による二酸化炭素光還元の高機能化
| Project/Area Number |
15F15070
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
葉 金花 国立研究開発法人物質・材料研究機構, 国際ナノアーキテクトニクス研究拠点, 主任研究者 (90230630)
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| Co-Investigator(Kenkyū-buntansha) |
ZHAO GUIXIA 国立研究開発法人物質・材料研究機構, 国際ナノアーキテクトニクス研究拠点, 外国人特別研究員
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| Project Period (FY) |
2015-07-29 – 2017-03-31
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| Keywords | Photocatalysis / Carbon nitride / CO2 reduction / H2 evolution |
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| Outline of Annual Research Achievements |
The project is mainly focused on exploring highly efficient photocatalysts for chemical fuel production based on visible-light responsive organic semiconductor, i.e. carbon nitride. Since the photo-generated electron-hole separation and transport is one of the main factors that limit the photocatalytic performance, we have conducted following researches to enhance the charge carrier separation and transport:
1) Constructing an imine-linked antenna-reaction center complex composed of low-molecular-weight carbon nitride and Co porphyrin, where the photogenerated electron-hole is expected to be separated more efficiently since electrons could be easily trapped by Co(II) to form Co(I) species and the active site immobilized on the C-N framework would facilitate the redox photocatalytic reaction;
2) Designing carbon nitride with enhanced in-planar ordering by controlling the self-assembly of heptazine precursors and calcination of the assembled precursors, where the intrachain transport and intraplanar transport of the photo-generated charge carriers is supposed to be largely enhanced.
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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 summary of the existing results, the structure morphology and element analysis indicate that we have successfully fabricated an antenna-reaction center complex based on carbon nitride and Co-porphyrin by a judicious condensation of low oligomeric carbon nitride and porphyrin and the following metallization of porphyrin ring. The performance evaluation results showed that the resulted complex showed enhanced photocatalytic CO2 reduction activity (17 umol/g/h) compared with that of bulk C3N4 (1.4 umol/g/h) and Co-porphyrin loaded C3N4 (7.2 umol/g/h). By combining the ESR and Semi-in situ UV-Vis absorption results, we inferred that in the complex, the interaction between heptazine-porphyrin network and Co(II) could induce a more delocalized Co(II) electronic structure. With irradiation, the photogenerated electron-hole could be separated more efficiently in the covalent bridged hybrid since electrons could be easily trapped by Co(II) to form Co(I) species, which is supposed energetically located closely to the conduction band. When CO2 happened to bind with Co porphyrin site, CO2 reduction can be occurred to form CO. It has been demonstrated that the covalent combination of light harvest antenna and active sites plays a great role in promoting photocatalytic activity, which would inspire more ingenious designings of photocatalytic system. The main results have been arranged into one manuscript that has been submitted for publication.
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| Strategy for Future Research Activity |
In the next step, we plan to further design carbon nitride with enhanced in-planar ordering by controlling the self-assembly of heptazine precursors and calcination of the assembled precursors. It is challenging to control the self-assembly of heptazine precursors by adjusting the solvents and the temperatures, as well as the further calcination to transform the highly ordered heptazine precursors into poly(tri-s-triazine) with improved in-planar ordering. With the aid of XRD, SEM and TEM, the assembly condition for heptazine unit can be optimized. And the calcination condition for the assembled precursors will be optimized by combining XRD, BET analysis, UV-Vis absorption measurement, photoelectrochemical test and the H2-evolution performance evaluation of the resulted carbon nitride. It is expected that novel carbon nitride with improved in-planar ordering and accelerated charge transport and separation will be obtained and show efficient activity in photocatalytic H2 evolution.
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Research Products
(2 results)
