Direct and real-time observation of hole transport dynamics in anatase TiO2 using X-ray free-electron laser

Sang Han Park, Abhishek Katoch, Keun Hwa Chae, Sanjeev Gautam, Piter Miedema, Sang Wan Cho, Minseok Kim, Ru Pan Wang, Masoud Lazemi, Frank de Groot, Soonnam Kwon

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Carrier dynamics affects photocatalytic systems, but direct and real-time observations in an element-specific and energy-level-specific manner are challenging. In this study, we demonstrate that the dynamics of photo-generated holes in metal oxides can be directly probed by using femtosecond X-ray absorption spectroscopy at an X-ray free-electron laser. We identify the energy level and life time of holes with a long life time (230 pico-seconds) in nano-crystal materials. We also observe that trapped holes show an energy distribution in the bandgap region with a formation time of 0.3 pico-seconds and a decay time of 8.0 pico-seconds at room temperature. We corroborate the dynamics of the electrons by using X-ray absorption spectroscopy at the metal L-edges in a consistent explanation with that of the holes.

Original languageEnglish
Article number2531
JournalNature communications
Issue number1
Publication statusPublished - 2022 Dec

Bibliographical note

Funding Information:
We appreciate professor K. R. Wee for his support in supply of the materials and advices. We would like to thank the PAL management. The technical support by the XFEL accelerator and beamline divisions are gratefully acknowledged. This work is supported by the National Research Foundation (NRF-2020R1A2C1007416 for S.K., NRF-2020R1C1C1009007 for K.R.W., NRF-2018R1D1A1B07046676 for S.H.P.) of South Korea.

Publisher Copyright:
© 2022, The Author(s).

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • General
  • Physics and Astronomy(all)


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