ELECTROCHEMICAL-BEHAVIOR OF AMINO-ACIDS ON PT(H,K,L) - A VOLTAMMETRICAND IN-SITU FTIR STUDY .2. SERINE AND ALANINE ON PT(111)

A spectroelectrochemical study of the adsorption and oxidation of seri ne and alanine on Pt(111) electrodes has been carried out in 0.1 M HCl O4 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, adsor bed cyanide is detected at potentials above 0.4 V, whereas a higher po tential is needed in the case of alanine. Linear and multibonded CO ha ve also been detected as poisoning species during serine oxidation. Th ese adsorbed species have been isolated by irreversible adsorption exp eriments of amino acids. Dissolved CO2 has been found by FTIR spectros copy as an oxidation product of both amino acids. The role played by t he R group in the electrochemical behaviour of these molecules is sign ificant. Reversibly adsorbed serinate and alaninate anions have been a lso detected. As in the case of the anions present in glycine solution s, the serinate and alaninate anions are two-fold coordinated to the P t(111) surface through the carboxylate group. (C) 1997 Elsevier Scienc e S.A.