水分解光触媒における助触媒中の 光励起ホール注入ダイナミクスの可視化に成功 〜共ドープが下ろす『かんぬき』が助触媒に渡ったホールの寿命を約16倍に〜

2026-05-19 高エネルギー加速器研究機構,東京科学大学

本研究の概念図。半導体光触媒（球体）に紫外光（紫色）を照射すると光励起ホールが生成し、表面に担持された酸化イリジウム助触媒（紫＋赤）に注入される。放射光X線パルス（黄色）を用いた時間分解X線吸収分光により、助触媒中のホール動態をナノ秒の時間スケールで直接観測した。

＜関連情報＞

• https://www.kek.jp/ja/press/202605191400
• https://pubs.acs.org/doi/10.1021/acscatal.6c02061

時間分解X線吸収微細構造分光による、水酸化反応用助触媒における光励起ホール注入ダイナミクスと電荷キャリア動態の解明 Time-Resolved X-ray Absorption Fine Structure Reveals Hole Injection Dynamics and Charge Carrier Kinetics in Cocatalysts for Water Oxidation

Tomoki Kanazawa,Chomponoot Suppaso,Issei Yamamoto,Dongxiao Fan,Rie Haruki,Ryo Fukaya,Kazuhiko Maeda,Shin-ichi Adachi,and Shunsuke Nozawa
ACS Catalysis  Published May 13, 2026
DOI:https://doi.org/10.1021/acscatal.6c02061

Abstract

Despite the criticality of photocarrier injection from semiconductor-based photocatalysts to cocatalysts in photocatalytic water splitting, carrier dynamics within cocatalysts remain poorly understood. To overcome the limitations of existing methods, which fail to separate semiconductor and cocatalyst signals, we used synchrotron-based time-resolved X-ray absorption fine structure spectroscopy to observe the injection of photoexcited holes from a semiconductor photocatalyst (TiO₂) to a cocatalyst (IrO_x) in real time. The oxidation of the Ir centers in IrO_x supported on TiO₂ or N,F-codoped TiO₂ (TiO₂:N,F) after excitation by ultraviolet light provided direct evidence for hole injection dynamics. The decay kinetics of the transferred holes in IrO_x revealed that the hole lifetime in IrO_x/TiO₂:N,F was ∼16 times longer than that in IrO_x/TiO₂, which was directly correlated with the higher photocatalytic water oxidation activity of the latter system. Our findings highlight the importance of the interfacial energy landscape in the design of photocatalyst systems, as it critically influences carrier lifetime in cocatalysts and promotes efficient charge separation to enhance photocatalytic performance.