Surface analysis of electrodes by ultra-high vacuum techniques: acetonitrile solvent chemisorption at Pt(111)

Abstract

Electrochemical studies at a carefully characterized Pt(111) electrode surface are yielding useful insights into atomic, ionic and molecular electrochemistry at interfaces. Reviewed here are studies of the chemisorption of the common polar aprotic solvent acetonitrile (CH 3CN) at a Pt(111) surface. Electrosorption of CH 3CN under typical electrolytic conditions from CH 3CN electrolyte, CH 3CN aqueous electrolytic solutions and CH 3CN vapor was investigated by high-resolution electron energy-loss spectroscopy (HREELS, vibrational spectroscopy), Auger electron spectroscopy (AES, elemental analysis), low-energy electron-diffraction (LEED, structure/symmetry probing) and linear potential scan cyclic voltammetry ( cv, exploration of electrochemical maturity). The results indicate that a chemisorbed layer is formed from CH 3CN liquid, vapor and typical aqueous solutions. The chemisorbed layer consists of a mixture of species related to CH 3CN and acetamide (CH 3CONH 2), contains about θ = 0.15 molecules per surface Pt atom is stable in vacuum and in solution over a wide range of electrode potentials, is replaced only slowly by other strong adsorbates such as iodide and lacks long-range order in the absence of anions such as iodide. Related studies are exploring ionic absorption, organic molecular adsorption and electrodeposition of metallic monolayers. A brief overview and references are included.