Real-time observation of photocatalytic reaction at solid-liquid interface by using wavelength-dispersive soft X-ray absorption spectroscopy

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K22475
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0401:Materials engineering, chemical engineering, and related fields
• Research Institution: High Energy Accelerator Research Organization
• Principal Investigator: Sakata Kaoruho 大学共同利用機関法人高エネルギー加速器研究機構, 物質構造科学研究所, 博士研究員 (80514215)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: 軟X線吸収分光 / 電気化学反応 / 光触媒 / リアルタイム測定

Outline of Final Research Achievements

In this study, a liquid cell was prepared aiming for a real-time observation of the photoelectrochemical reactions (oxygen evolution reaction) of semiconductor photocatalyst at solid/liquid interface by using the wavelength-dispersive X-ray absorption spectroscopy (XAS) in soft X-ray region. For the further improvement of the photocatalytic performance, it would be significant to clarify the reaction mechanism of the catalyst at solid/liquid interface.
The liquid part was separated from the measurement chamber in vacuum by using ultrathin Si3N4 window. An electrodes with TiO2 thin film was laminated onto the Si3N4 window attached with Pt thin film conductive layer. The electrode potential was swept to positive direction with/without illuminating UV light (wavelength 365 nm), and we succeeded to observed the XAFS spectra of oxygen K-edge (around 531 eV) of TiO2 during the electrode potential sweep, in real time.

Free Research Field

表面界面物性, 軟X線吸収分光, 電気化学

Academic Significance and Societal Importance of the Research Achievements

軟X線吸収分光は化学種の同定や金属酸化物半導体の電子状態の観察ができる強力な手法だが、通常は真空中での測定に限られるため、電位を印加した状態で固液界面の光触媒反応時の電子状態をoperando解析した研究はこれまでにほとんど無く、特色がある。さらに、本研究では、触媒と溶液の界面近傍における軟X線の吸収スペクトルを，触媒の動作中に秒を切る時間分解能で連続測定することで、電気化学測定中の光の照射のon/offや電位の掃引に対する、半導体光触媒電極表面の非定常な反応過程についての知見が得られることが期待される。