Following Adsorption Kinetics at Electrolyte/Metal Interfaces through Crystal Truncation Scattering: Sulfur on Au(111)

Combining electrochemical methods, in situ scanning tunneling microscopy, and surface x-ray diffraction allowed study of the structure and kinetics of $\mathrm{S}/\mathrm{A}\mathrm{u}(111)$ electrodes in aqueous electrolytes under potential control. Integrated intensities of a particular crystal truncation rod at anti-Bragg conditions were used to trace the sulfur adsorption and desorption as a function of electrode potential in real time. The S desorption is a first order process and the adsorption follows a Langmuir isotherm. A weakly bound S layer is found on the surface before charge transfer, and then specific adsorption occurs.