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

• DOI: 10.1038/s41467-022-30336-1
• Publication Date: 2022-05-09T10:03:05Z
• Authors: 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
• Keywords: 0301 basic medicine; 0303 health sciences; 03 medical and health sciences; Science; General Biochemistry,Genetics and Molecular Biology; Q; General Physics and Astronomy; General Chemistry; General; 01 natural sciences; Article; 0104 chemical sciences

AbstractCarrier 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.