2021 Fiscal Year Annual Research Report
Development of visible-light-driven photocatalysts via an interfacial photoexcitation process
| Project/Area Number |
21J12070
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
WARDHANA AUFANDRA CAKRA 東京工業大学, 物質理工学院, 特別研究員(DC2)
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| Project Period (FY) |
2021-04-28 – 2023-03-31
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| Keywords | Interfacial excitation / Photocatalyst / KPFM / Photodeposition / Thin film |
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| Outline of Annual Research Achievements |
Visible-light-driven interfacial charge transfer between first-row transition metal oxides and UV-driven semiconductors has been elucidated using a Cr2O3 ultrathin film coated on a SrTiO3 substrate as a photocatalyst model. This well-defined structure was prepared by a PLD and laser writing method. KPFM measurement suggested that electrons were excited from Cr2O3 thin film into SrTiO3 substrate through the interface (i.e. interfacial charge transfer/IFCT), thus leaving holes on the thin film. Holes mean free path from the interface to the surface of Cr2O3 was estimated to be within 90 nm. In addition, the excited electrons and holes were validated via a photodeposition of Au and MnOx, respectively. It turns out that Cr2O3 served as the oxidation site, while SrTiO3 was indicated as the reduction site. The reduction and oxidation sites were thus observed to be in proximity. From this study, we concluded that electrons were excited directly from the valence band of Cr2O3 to the conduction band of SrTiO3. It is noteworthy that both SrTiO3 and Cr2O3 are wide-gap semiconductors, thus only active under UV irradiation. However, when both semiconductors were combined, the direct interfacial excitation facilitates the visible-light activity. This study provides an insight into the development of efficient visible-light-sensitive photocatalysts driven by interfacial excitation.
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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
1. Cr2O3/SrTiO3 thin film system was successfully prepared by PLD. However, we found a difficulty to prepare the patterned thin film due to the unavailability of facility. Therefore, we used a laser writing process instead.
2. The set-up of KPFM was completely done. Also, the work with visible-laser irradiation on Cr2O3/SrTiO3 and CuO/SrTiO3 system led to a clear elucidation of IFCT (RBCT and BOCT) in the systems.
3. Both reduction and oxidation site were clearly observed by the photodeposition of Au and MnOx, respectively. In addition, oxygen (18O2) evolution from isotope water (H218O) during the Au photodeposition was observed by GC-MS. The successful verification of both reduction and oxidation site by observing the precipitated materials using AFM has led to a clearer understanding of RBCT.
4. Simulation on IFCT needs to be studied further in the future to elucidate this novel mechanism theoretically. In this moment, the combination of KPFM and photodeposition are powerful enough to elucidate the mechanism.
5. A paper and two conferences have been published on the basis of this work.
Overall, this work followed the scheduled I planned.
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| Strategy for Future Research Activity |
An h-type cell with a three-electrode configuration system (i.e., anode, cathode, and reference electrode) will be used to study a photo/electrochemical properties of interfacial charge transfer (IFCT). The bias potential may also be applied to the system. Currently, a photoelectrochemical system with a single photoelectrode, either using BOCT-driven photocathode or RBCT-driven photoanode, is under study. After they are satisfactorily studied, a z-scheme configuration consists of both photoelectrodes may be constructed.
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Research Products
(3 results)
