Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 40: Surface Dynamics

O 40.6: Vortrag

Dienstag, 18. März 2025, 15:15–15:30, H6

Photo-induced carrier and structural dynamics in anatase TiO₂ nanosheets — •Zhipeng Huang^1,2, Yan Yan², Xinxin Cheng^2,3, R. J. Dwayne Miller⁴, and R. Kramer Campen¹ — ¹Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen — ²Max Planck Institute for the Structure and Dynamics of Matter — ³SLAC National Accelerator Laboratory — ⁴Departments of Chemistry and Physics, University of Toronto

Ultrathin anatase TiO₂ nanosheets with {001} facets have significantly higher activity for light-induced H₂ evolution than other TiO₂-based materials. The mechanism of this enhancement is not understood. Gaining such insight requires understanding the dynamics of charge carriers and their interactions with lattices after optical excitation. Here we characterize structural and charge carrier dynamics in these materials following UV excitation using ultrafast electron diffraction and transient absorption spectroscopy.

We observed an ultrafast lattice expansion and distortion in the nanosheets, occurring earlier than the Debye-Waller effect. Density Functional Theory (DFT) calculations suggest that the lattice expansion and distortion are induced by the trapping of charge carriers and the formation of large electron polarons. Compared to TiO₂ nanoparticles, the nanosheets exhibit significantly higher polaron populations, which explains their enhanced photocatalytic properties.

Keywords: Ultrafast Electron Diffraction; Electronic Excitation; Carrier and Lattice Dynamics; Polaron formation and dynamics