SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 81: Oxide and Insulator Surfaces I: Adsorption and Reaction of Small Molecules

O 81.10: Vortrag

Donnerstag, 30. März 2023, 17:15–17:30, CHE 91

Identification of Intermediates in the Reaction Pathway of SO2 on the CaO surface: From Physisorption to Sulfite to Sulfate — •Nils Schewe¹, Farahnaz Maleki², Giovanni Di Liberto², Hicham Idriss¹, Gianfranco Pacchioni², and Christoph Wöll¹ — ¹Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344, Germany — ²Department of Materials Science, University of Milano-Bicocca, 20125 Milano, Italy

We report on the results of a combined experimental and theoretical study of the interaction of sulfur dioxide with a calcium oxide single crystal surface. Our investigation of this model system for flue gas desulfurization was carried out on the CaO (001) surface under ultra-high-vacuum conditions. Combining UHV infrared reflection absorption spectroscopy (IRRAS) with x-ray photo electron spectroscopy (XPS) and ab initio density functional theory (DFT) calculations, we were able to identify a three-step reaction path way. After the physisorption of SO2 at temperatures below 70 K on the ubiquitously hydroxylated surface, increasing the temperature leads to insertion of the SO2 into surface hydroxyl groups. Around 110 K the first insertion leads to a surface hydrogen-sulfite, which evolves into a surface hydrogen-sulfate with the second insertion into another OH-group above 160 K. The surface state was confirmed by DFT, where the predicted IR vibrational frequencies align with the experimentally observed ones.