Abstract: Amino acids are the building blocks of peptides and proteins. An amino acid molecule contains multi-functional groups such as —COOH, —NH₂, —OH and —CH_x, which leads to the amino acids to be used often as model reagents in surface electrochemistry and electrocatalysis, for the purpose of obtaining information about the interaction of different functional groups with electrocatalyst surfaces and the role of these functional groups in electrocatalysis of small organic fuels. Up to now, the reaction mechanism of amino acid electrooxidation is still far to be well understood. In this study, adsorption and oxidation of L-lysine on electrodes of nanometer scale thin film of gold in alkaline solutions were investigated using in situ FTIR reflection spectroscopy and electrochemical methods. The FTIRS result demonstrate that the dissociative adsorption of lysine on Au surface can occur in a low potential region, and the chemisorbed species were identified as adsorbed CN^- species(cyanide, 2110 cm^-1). Another reversibly(or loosely) adsorbed species may be the deprotonated amino acids, which were bound to the surface by both oxygen atoms of carboxyl group. When electrode potential is higher than 0.1 V, the adsorbed CN^- can be oxidized to NCO^-(2254 cm^-1); when electrode potential is above 0.3 V, OCN^-(cyanate, 2168 cm^-1) appeared as oxidative species; and when the potential is increased further up to 0.5 V, another further oxidative species, the AuCN species(gold cyanide, 2226 cm^-1) appeared. This study is of importance in understanding the interaction between amino acids and Au film electrodes.

Key words: L-Lysine, Nanometer scale Au film electrode, Adsorption, Oxidation, in situ FTIRS