Hole Dynamics in Photoexcited Hematite Studied with Femtosecond Oxygen K-edge X-ray Absorption Spectroscopy

Yohei Uemura; Ahmed S M Ismail; Sang Han Park; Soonnam Kwon; Minseok Kim; Hebatalla Elnaggar; Federica Frati; Hiroki Wadati; Yasuyuki Hirata; Yujun Zhang; Kohei Yamagami; Susumu Yamamoto; Iwao Matsuda; Ufuk Halisdemir; Gertjan Koster; Christopher Milne; Markus Ammann; Bert M Weckhuysen; Frank M F de Groot

doi:10.1021/acs.jpclett.2c00295

Hole Dynamics in Photoexcited Hematite Studied with Femtosecond Oxygen K-edge X-ray Absorption Spectroscopy

J Phys Chem Lett. 2022 May 19;13(19):4207-4214. doi: 10.1021/acs.jpclett.2c00295. Epub 2022 May 5.

Authors

Yohei Uemura^{1

2

3}, Ahmed S M Ismail¹, Sang Han Park⁴, Soonnam Kwon⁴, Minseok Kim⁴, Hebatalla Elnaggar¹, Federica Frati¹, Hiroki Wadati^{5

6}, Yasuyuki Hirata⁵, Yujun Zhang⁵, Kohei Yamagami⁵, Susumu Yamamoto⁵, Iwao Matsuda⁵, Ufuk Halisdemir⁷, Gertjan Koster⁷, Christopher Milne^{3

8}, Markus Ammann², Bert M Weckhuysen¹, Frank M F de Groot¹

Affiliations

¹ Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitslaan 99, Utrecht, 3584 CG, The Netherlands.
² Laboratory of Environmental Chemistry, Energy and Environment Research Division, Paul Scherrer Institut, Villigen, 5232, Switzerland.
³ European XFEL, Holzkoppel 4, Schenefeld, 22869, Germany.
⁴ PAL-XFEL, Pohang Accelerator Laboratory, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, South Korea.
⁵ Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
⁶ Graduate School of Material Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan.
⁷ Faculty of Science and Technology and MESA + Institute for Nanotechnology, University of Twente, P.O. Box 2171, Enschede, 7500 AE, The Netherlands.
⁸ SwissFEL, Paul Scherrer Institut, Villigen, 5232, Switzerland.

Abstract

Hematite (α-Fe₂O₃) is a photoelectrode for the water splitting process because of its relatively narrow bandgap and abundance in the earth's crust. In this study, the photoexcited state of a hematite thin film was investigated with femtosecond oxygen K-edge X-ray absorption spectroscopy (XAS) at the PAL-XFEL in order to follow the dynamics of its photoexcited states. The 200 fs decay time of the hole state in the valence band was observed via its corresponding XAS feature.