SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 101: Poster Session VIII: Oxides and insulators: Adsorption and reaction of small molecules II
O 101.8: Poster
Donnerstag, 4. März 2021, 13:30–15:30, P
Surface reactivity to hydrogen of Ag- and Cu- modified CeO2 — •Stefania Benedetti1, Avinash Vikatakavi1,2, Giulia Righi1,2, Paola Luches1, Sergio D'Addato1,2, Rita Magri1,2, and Annabella Selloni3 — 1CNR, Instituto Nanoscienze, 41125 Modena, Italy — 2Dipartimento di Fisica, Informatica e Matematica, Universita' di Modena e Reggio-Emilia, 41125 Modena, Italy — 3Department of Chemistry, Princeton University, Princeton, New Jersey 08540, United States
In this work we investigate the H2 dissociation on Ag- and Cu- modified CeO2 surfaces to increase oxide activity for application in catalytic reactions in electrochemical devices to replace Pt. We have followed by XPS the Ag oxidation state, the concentration of Ce3+ ions, O vacancies, and OH- groups during thermal reduction cycles in H2 and in UHV of thin CeO2 films. As expected, the reactivity of ceria toward H2 dissociation improves when Ag is included. However, thermal treatment under H exposure decreases the concentration of Ce3+ ions in Ag-modified ceria with respect to pure oxide in the same conditions, while the number of surface O vacancies is larger for the Ag-modified surface [1]. Thanks to DFT calculations, we explain this behavior in terms of a reduction of the surface Ag, which acquires some of the extra electrons created by the O vacancies and the adsorbed H atoms. Results are compared to films with substitutional Cu atoms. In this case Ce3+ concentration increases by a factor of 2 compared to pure oxide and activation temperature decreases to 570 K. [1] S. Benedetti et al., ACS Applied Materials & Interfaces, 2020, 12, 24, 27682-27690