Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 78: Poster: Surface Dynamics - Reactions, Elementary Processes and Phase Transitions

O 78.6: Poster

Wednesday, March 14, 2018, 18:15–20:30, Poster A

Dynamics and reactivity of long-lived excess electrons in DMSO films on Cu(111) — •Angelika Demling, Sarah B. King, Katharina Broch, and Julia Stähler — Department of Physical Chemistry, Fritz Haber Institute of the MPG, Faradayweg 4-6, 14195 Berlin, Germany

DMSO is a widely used non-aqueous solvent with the potential to be used in lithium-oxygen batteries due to its ability to catalyze the superoxide formation and to stabilize the products. In this work we investigate the electron dynamics in DMSO films on Cu(111) using time-resolved two-photon photoemission. We show that films of a thickness > 2 monolayers exhibit two surface-bound electronic states at 2.41 ± 0.05 eV and 2.30 ± 0.05 eV above the Fermi level with lifetimes on the order of several seconds. Both are formed from the same precursor state, a small polaron in the second monolayer. Due to their long lifetime and binding location on the DMSO surface, we assign these states to electrons residing in deep traps at the DMSO/vacuum interface. Moreover, the photoemission signal from the trapped electrons decreases and the work function increases over time under illumination. Both effects are disscussed as possible results of light-induced reorganization of molecules at the surface. Further experiments in an oxygen atmosphere suggest the surface-bound electrons react with oxygen, making these findings of high relevance for the understanding of the formation of superoxide in lithium-oxygen batteries.