THE EFFECT OF THE STRUCTURAL AND MORPHOLOGICAL PROPERTIES OF THE SURFACE OF PLATINUM ON THE KINETIC AND THERMODYNAMIC CHARACTERISTICS OF THE SERINE ANION ADSORPTION PROCESS

Abstract

Purpose. The purpose of this paper is to establish the infl uence of the differences in the structural and morphological properties of the surface of Pt and Pt(Pt) electrodes (roughness, in particular) on the basic principles and thermodynamic characteristics of the adsorption process of serine anion. Methods and methodology. Kinetic isotherms of adsorption of serine anion on a smooth and platinized platinum electrode were obtained by electrooxidation in the adsorbed layer (charging curves). The true surface area of the corresponding platinum electrode was calculated using the charge in the desorption region of atomic hydrogen. The adsorption potential was selected following the results of linear voltammetry. The criterion for selection was the absence of the oxidation/reduction process of the amino acid anion. It was found that the process of adsorption of serine anion on platinum can be described by the logarithmic Temkin isotherm on an energetically uniformly inhomogeneous surface, and the adsorption kinetics can be described by the Roginsky–Zeldovich equation. Adsorption on a Pt(Pt) electrode is accompanied by serine dissociation, whereas adsorption on smooth platinum is non-dissociative. Results. The calculated energetically inhomogeneity factor of the platinized platinum electrode surface is almost twice as high as that of a smooth Pt surface. Such high values indicate a signifi cant difference in the binding energy between platinum atoms and anions of serine. Conclusions. The standard Gibbs energy and the equilibrium constants were calculated for the processes of exchange dissociative and non-dissociative adsorption of serine on a smooth surface and platinized Pt respectively. The obtained values indicate the chemical nature of the dominant forces of interaction between anions of serine and the surface of the platinum electrode.

Keywords

• serine
• amino acid
• platinum
• adsorption
• isotherm.