Effect of coating by perfluorosulfonated ionomer film on electrochemical behaviors of Pt(111) electrode in acidic solutions

Electrochemical behaviors of bare and perfluorosulfonated ionomer (PFSI) film-coated Pt(111) electrodes in perchloric and sulfuric acid solutions were investigated. While current peaks corresponding to specific adsorption and desorption of anions were clearly observed at the bare electrode, no such peaks were observed at the PFSI-coated electrode, showing that anions do not reach the electrode surface because of the cation-selective nature and/or adsorption of PFSI film. Although no structural change was observed by repetitive potential cycling as far as positive potential limit was more negative than that of oxide formation, significant structural change was noticed during potential cycling if the anodic potential limit was made more positive than oxide formation potential

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

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 x √3) structure took place at around +130 mV. The Ag bilayer and Cl^[-] ions were oxidatively reacted to form the AgCl monolayer with (√13 x √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 x √13)R13.9° structure to (4 x 4) structure around +500 mV. When the potential was scanned back negatively, the AgCl monolayer was electrochemically reduced, and a Ag monolayer, not a bilayer, was formed on the Au(111) surface. In the subsequent potential cycles, the structural change between the Ag monolayer and the AgCl monolayer was reversibly observed. All oxidative structural changes were much slower than the reductive ones