A transfer cell for ultra-high vacuum surface analysis of samples exposed to electrochemical environments

We present the design and implementation of a portable transfer system equipped with an integrated electrochemical cell that enables the controlled transfer of samples between an electrochemical environment and an ultra-high vacuum (UHV) system without air exposure. This setup allows for the preparation of well-defined model surfaces, their electrochemical modification, and subsequent structural and chemical characterization using surface-sensitive UHV techniques. The system's performance was validated using Au(111) as a model electrode. Cyclic voltammetry performed in a hanging meniscus configuration reproduced the characteristic oxidation and reduction features of Au(111), while scanning tunneling microscopy, low-energy electron diffraction, and Auger electron spectroscopy confirmed the structural and chemical integrity of the surface after transfer. Progressive surface roughening with increasing numbers of oxidation-reduction cycles followed an approximately linear trend, consistent with previous studies. Additionally, we investigated the stability of gold oxide under vacuum and demonstrated that the thin oxide formed during anodic polarization, prior to the onset of the oxygen evolution reaction, is partially reduced during UHV transfer. X-Ray Photoelectron Spectroscopy and Auger spectroscopy data indicate that the oxidized phase is stable in vacuum only after polarization at sufficiently high potentials, when continuous oxygen evolution is achieved via water electrolysis. Finally, successful integration and testing of the system at the FlexPES beamline at MAX IV confirmed its compatibility with synchrotron-based spectroscopy.