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O: Fachverband Oberflächenphysik

O 88: Poster Session VII: Oxides and insulators: Adsorption and reaction of small molecules I

O 88.7: Poster

Donnerstag, 4. März 2021, 10:30–12:30, P

Real-time Dynamics During TiO₂ Photocatalysis — •Michael Wagstaffe¹, Lukas Wenthaus^1,2, Adrian Dominguez-Castro³, Thomas Frauenheim^3,4,5, Adriel Dominguez³, Angel Rubio^2,6, Wilfried Wurth^1,2,7, Andreas Stierle^1,7, and Heshmat Noei¹ — ¹DESY, 22607, Hamburg, Germany — ²CFEL, 22761, Hamburg, Germany — ³BCCMS, 28359, Bremen, Germany — ⁴CSAR, 518110, Shenzhen, China — ⁵CSRC, 100193, Beijing, China — ⁶MPI for the Structure and Dynamics of Matter, 22761, Hamburg, Germany — ⁷Fachbereich Physik Universität Hamburg, 20355, Hamburg, Germany

Studies of photocatalytic reactions on TiO₂ are instrumental to the development of technology used for self-cleaning surfaces and for air and water purification. We utilize femtosecond X-ray laser pulses synchronized with an optical laser to directly follow the reaction dynamics of the photooxidation of CO on the anatase TiO₂(101) surface. Our time-resolved soft X-ray photoemission spectroscopy results, combined with theoretical calculations, allow us to elucidate the mechanism of oxygen activation and provides evidence of ultrafast timescales. The reaction takes place between 1.2 - 2.8 (± 0.2) ps after irradiation with an ultrashort laser pulse, resulting in CO₂. No intermediate species were observed on a picosecond time scale. Theoretical calculations predict that the reaction can be initiated following the formation an O₂-TiO₂ charge-transfer complex. This allows the reaction to take place following laser illumination at a photon energy of 1.6 eV (770 nm), following the direct transfer of electrons from TiO₂ to physisorbed O₂.