Defect-engineering for the development of highly active photocatalysts

2022 Fiscal Year Final Research Report

• Project/Area Number: 19H02820
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 36020:Energy-related chemistry
• Research Institution: Okayama University (2021-2022); Toyota Technological Institute (2019-2020)
• Principal Investigator: Yamakata Akira 岡山大学, 自然科学学域, 教授 (60321915)
• Co-Investigator(Kenkyū-buntansha): 酒多 喜久 山口大学, 大学院創成科学研究科, 教授 (40211263)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 光触媒 / 光励起キャリアダイナミクス / 再結合 / 時間分解分光計測 / 水分解光触媒 / 可視光応答型光触媒

Outline of Final Research Achievements

It has been widely believed that the defects decrease the photocatalytic activity. However, our resent results revealed that the defects can elongate the lifetime of photogenerated charge carriers and hence could be useful to increase the activity. However, these opposite effects of the defects on the photocatalytic activity has not been elucidated yet. In this work, we have investigated the effects of the defects on the recombination kinetics for a number of materials by using time-resolved absorption spectroscopy. We found that the formation of oxygen vacancies accelerates the recombination in which the oxygen vacancies tend to get closed to each other such as nonstoichiometric oxide. However, other materials which hardly form oxygen vacancies, the rate of recombination was prevented. The difference in the distance between the oxygen vacancies determines the effects on the photocatalytic activity.

Free Research Field

表面分光学

Academic Significance and Societal Importance of the Research Achievements

光触媒を用いると太陽エネルギーを使って水から水素を製造できる。太陽電池を使った水の電気分解に比べてこの方法の優れたところは、光触媒の方が太陽電池よりも製造コストが安いため、より安価に水素を製造できることにある。しかし、粉末の表面には欠陥が多数存在し、これらの欠陥は光励起キャリアを捕捉し、再結合を促進するので、光触媒活性を低下させる最大の原因であると考えられてきた。しかし、申請者のこれまでの研究により、表面欠陥はむしろ光触媒活性の向上に役立つ場合があることが分かった。そこで、この原理を積極的に利用し、従来の“定説”とは逆に欠陥を有効に利用するところに本研究の学術的な意義がある。