Surface electrochemical studies of nitrogen-containing compounds, sulfur-containing compounds and iodine chemisorbed at gold

Abstract

The interactions of smooth polycrystalline Au electrodes with 3,6- dihydroxypyridazine (DHPz), 2,3-dihydroxypyridine (DHPy), pentafluorothiophenol (PFT), 2,5-dihydroxy-4-methylbenzylmercaptan (DMBM), and 2,5-dihydroxythiophenol (DHT) were studied using thin-layer electrochemistry. The surface coverage of DHPz and DHPy was found to be pH dependent. In-situ Fourier transform infrared reflectance absorbance spectroscopy (FTIRRAS) of DHT showed that the diphenol/quinone moiety retains its electrochemical reactivity and oxidizes to CO₂ at potentials higher than 0.8 V vs. AgCl. The structure and composition of iodine adsorbed on polvcrystalline and single crystal Au (111) was determined by thin-layer electrochemistry and a combination of surface spectroscopic techniques [low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and Xray photoelectron spectroscopy (XPS)]. Adsorbate substitution and competitive chemisorption experiments between iodine and the sulfur moiety of DHT at smooth polycrystalline Au electrodes were also done. By correlation with the electrochemical behavior, the strength of the chemisorption of adsorbed species at Au electrodes exhibited the following trend: iodine > sulfur-containing compounds > nitrogen-containing compounds.