Photoinduced anisotropic distortion as the electron trapping site of tungsten trioxide by ultrafast W L1-edge X-ray absorption spectroscopy with full potential multiple scattering calculations

• Published in: Physical chemistry chemical physics : PCCP 2020-02, Vol.22 (5), p.2615-2621
• Main Authors: Koide, Akihiro, Uemura, Yohei, Kido, Daiki, Wakisaka, Yuki, Takakusagi, Satoru, Ohtani, Bunsho, Niwa, Yasuhiro, Nozawa, Shunsuke, Ichiyanagi, Kohei, Fukaya, Ryo, Adachi, Shin-ichi, Katayama, Tetsuo, Togashi, Tadashi, Owada, Shigeki, Yabashi, Makina, Yamamoto, Yusaku, Katayama, Misaki, Hatada, Keisuke, Yokoyama, Toshihiko, Asakura, Kiyotaka
• Format: Article
• Language: English
• Subjects: Conduction bands; Delay time; Distortion; Electron states; Excitation; Fine structure; Free electron lasers; Mathematical analysis; Multiple scatter; Photocatalysis; Photocatalysts; Photoexcitation; Spectrum analysis; Tungsten; Water splitting; X ray absorption; X-ray spectroscopy
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp01332f

Understanding the excited state of photocatalysts is significant to improve their activity for water splitting reaction. X-ray absorption fine structure (XAFS) spectroscopy in X-ray free electron lasers (XFEL) is a powerful method to address dynamic changes in electronic states and structures of photocatalysts in the excited state in ultrafast short time scales. The ultrafast atomic-scale local structural change in photoexcited WO3 was observed by W L1 edge XAFS spectroscopy using an XFEL. An anisotropic local distortion around the W atom could reproduce well the spectral features at a delay time of 100 ps after photoexcitation based on full potential multiple scattering calculations. The distortion involved the movement of W to shrink the shortest W–O bonds and elongate the longest one. The movement of the W atom could be explained by the filling of the dxy and dzx orbitals, which were originally located at the bottom of the conduction band with photoexcited electrons.