Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)

O 35.59: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B1

Proton distribution and transfer at the titanate/water solid-liquid interface — •Christina Ebensperger, Christof Jäger, and Bernd Meyer — Interdisziplinäres Zentrum für Molekulare Materialien und Computer-Chemie-Centrum, Universität Erlangen-Nürnberg

Layered sodium titanates show a rich structural behavior in aqueous environments. Sodium ions dissolve and the surfaces become protonated. In acid solution single titanate layers can detach and nanoscrolls are formed. To obtain a more detailed understanding of the surface protonation we performed DFT calculations and Car-Parinello molecular dynamics simulations for sodium titanate surfaces in contact with vacuum, a monolayer of water molecules and a liquid water reservoir. We find that the energetical hierarchy of preferred protonation sites and the proton distribution depend on the environment and change from vacuum to thin water films and the solid-liquid interface. A full explicit treatment of the liquid surrounding is thus mandatory for obtaining realistic surface structures. In the CPMD simulations we observe water-mediated transfers of surface protons between different adsorption sites. In rare cases spontaneous de-protonation events of the surface occur, which may explain the negative surface charge observed in experiments.