Reflection mode X-ray absorption spectroscopy: new applications in surface science research

Reflection mode grazing incidence X-ray absorption spectroscopy (GIXAFS) was applied for the in situ investigation of solid/liquid interfaces. Results obtained during the active dissolution of metals are presented. In the case of silver in neutral or weakly acidic Na2SO4 solutions (pH 6.5), the formation of an Ag-O species at the surface of the Ag-electrode can be proven, i.e. the active dissolution proceeds via a non-protecting surface layer, the thickness of which was estimated to be about 5 nm. The atomic short-range order of this surface layer is different from polycrystalline silver oxides (Ag2O and AgO) and relates to a more disordered or amorphous Ag1+ oxide.