Unveiling mechanism of photocatalytic water splitting at water/photocatalyst interfaces

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H06029
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Physical chemistry
• Research Institution: Institute for Molecular Science (2018); Kyoto University (2016-2017)
• Principal Investigator: Sugimoto Toshiki 分子科学研究所, 物質分子科学研究領域, 准教授 (00630782)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 水分解光触媒 / 光誘起電荷ダイナミクス / 2次元水素結合系 / 赤外拡散反射分光 / 過渡吸収分光

Outline of Final Research Achievements

In this project, we have performed infrared transient and steady-state absorption spectroscopy of anatase TiO2 nanoparticles as a function of the number of water adsorbate layers. These absorption measurements in water vapor atmosphere have an advantage over those in liquid water because the number of water layers at the interface can be controlled by relative humidity. We showed that water adsorbates strongly interacting with substrate serve as effective hole traps, but the trapping ability is reduced by hydrogen bonding with other water molecules in the second layer. In addition, we have investigated the hole decay characteristics and photocatalytic activity of BiVO4 with single-particle transient absorption microscopy and found that grain boundaries in aggregated particles do not work as recombination centers but play an important role in elongation of carrier lifetime and thus in enhancing the reactivity of photocatalyst through trap-detrap processes.

Free Research Field

物理化学

Academic Significance and Societal Importance of the Research Achievements

本研究では，精密に圧力を制御した水蒸気雰囲気下で光触媒表面近傍のみを擬似的に水中環境下におくことができ，水溶液中では本来測定が不可能な振動分光を可能にした．さらに，反応と無関係な情報を含むスペクトル信号の中から反応活性ファクター(反応に寄与する表面構造・電子状態，水の水素構造に関する成分)を有効に抽出することによって光触媒/水界面における反応活性増大メカニズムの分子論的基礎を確立することができた．これにより，既存のバンドエンジニアリングで想定されている限界を超えた高量子効率を誇る光触媒の創製につながり，人工光合成分野の飛躍的発展が期待される．