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O: Fachverband Oberflächenphysik

O 52: Poster Wednesday: Adsorption and Catalysis 2

O 52.1: Poster

Mittwoch, 7. September 2022, 18:00–20:00, P4

Investigation of the influence of the spin in adsorption structures of oxygen on a cerium chloride catalyst surface in the Deacon process using computational methods — •Kathrin Nieswiec and Franziska Hess — Technische Universität Berlin, Institut für Chemie, Straße des 17. Juni 124, 10623 Berlin, Germany

CeO2-based catalysts in the HCl oxidation undergo reversible deactivation by forming CeCl3. This works examines the interaction of the CeCl3-(110)-surface with O2 during the reoxidation of CeCl3. CeCl3 is an insulator, where Ce is 9-fold coordinated that exposes different adsorption sites at the surface. Different adsorption structures of atomic and molecular oxygen on the CeCl3-(110)-surface are examined in terms of energy, electronic state and magnetization. Cerium-based catalyst systems are investigated by DFT calculations in the PAW approach with the PBE functional including Hubbard-U correction. Ab-initio thermodynamics are employed to analyze temperature and pressure-dependency of oxygen adsorption on the surface. Upon adsorption of oxygen on the surface, Ce³⁺ can be locally oxidized to Ce⁴⁺, resulting in different spin and charge density distributions. Consequently, the adsorption energies of oxygen can variate by over 1 eV, depending on the initial spin state. The ab-initio thermodynamics analysis based on the obtained oxygen adsorption energies suggests that the CeCl3 surface is expected to be covered by oxygen due to the strong Ce-O bond. These results suggest that spin must be explicitly included when examining adsorption on CeCl3 surfaces in order to obtain correct adsorption energies for catalysis applications.