In situ X-ray scattering studies of growth at liquid metal - liquid electrolyte interfaces

• Applicant: Professor Dr. Olaf Magnussen
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Experimental Condensed Matter Physics
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 266661790

• Final Report Year: 2019

Final Report Abstract

In this project we further developed experimental approaches for in situ studies of nucleation and growth processes at liquid metal - liquid electrolyte interfaces on the atomic scale and employed those to selected model systems. In particular, we performed X-ray reflectivity and grazing incidence diffraction measurements of liquid Hg electrodes in NaCl, NaBr, and Na2B4O7 solutions. We demonstrated that the Hg surface layering is preserved in all electrolytes and depends only weakly on the anion species. For the growth of Pb halide layers via deamalgamation we observed in electrolytes containing (apart from Pb) only Cl or only Br anions a similar behavior as in our earlier studies of PbBrF growth, i.e., an initial formation of an ultrathin crystalline adlayer, which serves as a template for a subsequent “epitaxial” growth of three-dimensional crystallites. This suggests that the transient formation of such a precursor layer is a more general phenomenon in the growth of salt-like layers at these liquid-liquid interfaces. Furthermore, the electrochemical growth of Ge via the solid-liquid-liquid method was studied in cooperation with the Maldonado group. Here, no precursor layer could be observed, however, the formation of a distinct adlayer was found at the positive end of the double layer regime, which we tentatively assign to adsorbed HGeO 3-. In summary, these studies provided first systematic atomic-resolution data on adsorption and growth at liquid metal electrodes in electrochemical environment and thus should helped to establish synchrotron-based X-ray scattering studies as a tool for clarifying (electro-)chemical processes at these deeply-buried interfaces.

Publications

• Atomic scale structure of liquid metal - electrolyte interfaces, Nanoscale, 8, 13859-13866 (2016)
  B.M. Murphy, S. Festersen, O.M. Magnussen
  
• Temperature and potential dependent structure of the mercury-electrolyte interface, Phys. Rev. B, 93, 165408-1 - 165408-9 (2016)
  B. Runge, S. Festersen, C.T. Koops, A. Elsen, M. Deutsch, B.M. Ocko, O.H. Seeck, B.M. Murphy, O.M. Magnussen
  
• Strukturuntersuchungen an Flüssigkeitsgrenzflächen mittels Röntgenstreumethoden, Dissertation, Christian-Albrechts-Universität zu Kiel (2017)
  S. Festersen
  
• Investigating Solid –State and Liquid Interfaces on the Nanoscale with X-rays, Habilitation Thesis, Christian-Albrechts-Universität zu Kiel (2018)
  B. M. Murphy
  
• X-ray reflectivity from curved liquid interfaces, J. Synchrotron Rad., 25, 4132-438 (2018)
  S. Festersen, S.B. Hrkac, C.T. Koops,B. Runge, T. Dane, B.M. Murphy, O.M. Magnussen