Electrochemical behaviour of amino acids on Pt(h,k,l). A voltammetric and in situ FTIR study .2. Serine and alanine on Pt(111)

A spectroelectrochemical study of the adsorption and oxidation of serine and alanine on Pt(111) electrodes has been carried out in 0.1 M HClO4 solutions. From the voltammetric and FTIR spectroscopic results, we concluded that adsorbed cyanide is formed at the Pt(111) surface as a product of serine and alanine oxidation. In the case of serine, adsorbed cyanide is detected at potentials above 0.4 V, whereas a higher potential is needed in the case of alanine. Linear and multibonded CO have also been detected as poisoning species during serine oxidation. These adsorbed species have been isolated by irreversible adsorption experiments of amino acids. Dissolved CO2 has been found by FTIR spectroscopy as an oxidation product of both amino acids. The role played by the R group in the electrochemical behaviour of these molecules is significant. Reversibly adsorbed serinate and alaninate anions have been also detected. As in the case of the anions present in glycine solutions, the serinate and alaninate anions are two-fold coordinated to the Pt(111) surface through the carboxylate group. (C) 1997 Elsevier Science S.A.