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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
Thursday, March 4, 2021, 10:30–12:30, P
Real-time Dynamics During TiO2 Photocatalysis — •Michael Wagstaffe1, Lukas Wenthaus1,2, Adrian Dominguez-Castro3, Thomas Frauenheim3,4,5, Adriel Dominguez3, Angel Rubio2,6, Wilfried Wurth1,2,7, Andreas Stierle1,7, 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.