A spectroscopic investigation of the non-aqueous electrochemical double-layer in ultrahigh vacuum

Abstract

The research which will be presented on the combination of Raman spectroscopy with an ultrahigh vacuum (UHV) environment. The data show that UHV Raman spectroscopy is a useful analytical technique for modeling electrochemical interfaces. Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) were utilized to study the surface chemistry of 1-butanol and thiophenol. These molecules were studied on coldly-deposited and annealed Ag films grown in the UHV environment. Surface Raman studies of molecules adsorbed on coldly-deposited Ag films are abundant, because these films support significant surface Raman enhancement. However, recent advances in instrumentation make studies at relatively unenhancing annealed Ag films possible. Roughness and surface enhancement factors for coldly-deposited and annealed Ag surfaces were investigated using thiophenol. In addition, a correction factor was determined which allows data acquired in the UHV environment to be directly compared to data acquired in the laboratory ambient. Butanol orientation was studied at these Ag surfaces using Raman surface selection rules. The orientation of butanol is dictated by the solid-vacuum interface and the unique surface morphology present at these surfaces. Br and Na ions were used to model the interaction of butanol with electrolyte species found in normal electrochemical systems. The coverages of Br and Na were calibrated using XPS. The orientation of butanol was determined for varying coverages of these ions and compared the bare Ag surfaces. My research represents the first stages of modeling the electrochemical double-layer in the UHV environment using Raman spectroscopy.