Potential modulated reflectance study of the electrooxidation of simple amino acids on Pt(111) in acidic media

The electroreflectance (ER) technique has been applied to the study of the electrooxidation of some simple amino acids (glycine, serine and alanine) o n a Pt(111) surface in acid medium. A different behaviour in the (1/R)(part ial derivativeR/partial derivativeE) response as a function of applied pote ntial has been observed during the positive and negative scans as consequen ce of the formation of adsorbed cyanide originating from the oxidation of g lycine and serine. Alanine on the other hand does not readily form signific ant amounts of adsorbed cyanide on the first oxidation cycle. The integrate d ER spectra (DeltaR/R) of the three amino acids have also shown that the r eversible adsorption of the glycinate, serinate and alaninate anions is ini tiated at ca. 0.35 V and reaches maximum coverage at ca. 0.7 V. This revers ible adsorption produces changes in the reflectivity comparable to that dis played by bisulphate adsorption. (C) 2000 Elsevier Science S.A. All rights reserved.