| 研究課題/領域番号 |
21F21342
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| 配分区分 | 補助金 |
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| 研究機関 | 九州大学 |
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研究代表者 |
笹木 圭子 九州大学, 工学研究院, 教授 (30311525)
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| 研究分担者 |
SHENOY SULAKSHANA 九州大学, 工学(系)研究科(研究院), 外国人特別研究員
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| 研究期間 (年度) |
2021-11-18 – 2024-03-31
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| キーワード | Photocatalysis / graphitic carbon nitride / multi-metal oxide / CO2 reduction / solar fuels / heterojunction |
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| 研究実績の概要 |
The present study focuses on development of g-C3N4/multi-metal oxide semiconductors for photocatalysis applications (mainly CO2 reduction). Towards this end, g-C3N4 was synthesized in a polycondensation process (550oC, 2h) by employing urea as a precursor. CaFe2O4 is chosen among a large number of mixed metal oxides because of its strong visible light absorption efficiency (Eg ~ 1.9 eV) and compatible band edges with g-C3N4. Solution combustion synthesis approach was used to prepare CaFe2O4. In-situ reaction process was used to synthesize g-C3N4/CaFe2O4 composites. XRD confirmed the existence of both crystal phases in the synthesized photocatalysts without any impurity peaks. The bands of g-C3N4 (-NH2 stretching), (C-N and C=N) and triazine rings were intact after the addition of CaFe2O4 as confirmed from FTIR. Porous nanosheets of g-C3N4 are grown over CaFe2O4 particles as observed by SEM. The bandgap of g-C3N4 reduced from 2.65 to 2.45 eV after the addition of CaFe2O4. Complete photodegradation (100%) of ciprofloxacin and phenol was achieved within 30 and 120 min of light irradiation. The lower intensity PL peaks and smaller sized semicircle in the EIS plots confirmed the effective separation and transfer of charge carriers in g-C3N4/CaFe2O4. The valence band edges of g-C3N4 and CaFe2O4 obtained from XPS were 1.57 and 2.10 eV. The calculated conduction band edges from UV-DRS were -1.08 and 0.2 eV for g-C3N4 and CaFe2O4 respectively. The involvement of O2- radicals as main species in the degradation confirms that g-C3N4/CaFe2O4 forms direct Z-scheme heterostructure.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The literature study had previously been completed (during the quarantine period after entering Japan), allowing JSPS PDF to go right into the experiments once I arrived at Kyushu University. Practically all of the reagents and chemicals needed to prepare the photocatalysts were easily available in the lab. All of the characterization facilities are housed in the laboratory, which made it a lot easier to access them whenever needed. Most significantly, the communication between JSPS PDF and the host is smooth. Finally, but certainly not least, the fellow lab researchers are extremely helpful and willing to assist whenever needed. All of these situations have aided JSPS PDF in making excellent progress in the present research, and everything is proceeding according to plan.
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| 今後の研究の推進方策 |
Spinel structured ZnCo2O4 has superior electron conductivity and huge redox reaction sites. Its band edges are efficiently aligned with g-C3N4 to boost the photocatalytic activity. In the upcoming study, in-situ and solvo-thermal methods will be used to prepare composites of g-C3N4 with ZnCo2O4. The existence of both phases in the composite will be confirmed from XRD. The morphology and microstructure of g-C3N4/ZnCo2O4 will be explained on the basis of SEM and TEM observation. The surface elemental compositions and chemical states will be analyzed by XPS. The enhancement in the photo-absorption property of g-C3N4 after incorporation of ZnCo2O4 will be explained by UV-Vis DRS. During the photocatalytic CO2 reduction, pure CO2 gas will be purged into a reactor containing an aqueous solution of g-C3N4/ZnCo2O4 composite. Reaction will be carried out under 300 W Xe lamp λ> 400 nm, and the reaction products (CH4 and CO) will be analyzed using gas chromatography with He as the carrier gas. Recycle tests will be used to confirm the stability of g-C3N4/ZnCo2O4. The process of charge separation and transfer occurring at the interface between g-C3N4/ZnCo2O4 composite will be analyzed based on PL, EIS and photocurrent studies. Depending on the scavenger studies the main species responsible for CO2 reduction will be decided. The photogeneration of electron-hole pairs and their transportation at the g-C3N4/ZnCo2O4 interface and type of heterojunction formed will be discussed.
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