In Situ Electrochemical, Electrochemical Quartz Crystal Microbalance, Scanning Tunneling Microscopy, and Surface X-ray Scattering Studies on Ag/AgCl Reaction at the Underpotentially Deposited Ag Bilayer on the Au(111) Electrode Surface

Abstract

Ag/AgCl reaction at the Ag bilayer, which was underpotentially prepared on a Au(111) surface, was investigated using electrochemical quartz crystal microbalance (EQCM), scanning tunneling microscopy (STM), surface X-ray scattering (SXS), and electrochemical techniques. When the potential was scanned positively from −200 mV, the Cl– ion was adsorbed on the Au(111) electrode surface around 0 mV, and then the phase transition of the adsorbed Cl– ion layer from random orientation to (√3 × √3) structure took place at around +130 mV. The Ag bilayer and Cl– ions were oxidatively reacted to form the AgCl monolayer with (√13 × √13)R13.9° structure around +200 mV, accompanied with the formation of AgCl monocrystalline clusters on the AgCl monolayer surface. The structure of the AgCl monolayer on the Au(111) surface was changed from (√13 × √13)R13.9° structure to (4 × 4) structure around +500 mV. When the potential was scanned back negatively, the AgCl monolayer was electrochemically reduced, and a Ag monolayer, not...