Spectroelectrochemical study of picolinic acid adsorption during silver electrodeposition

Abstract

The adsorption of picolinic acid (PA) onto HOPG electrodes during silver electrodeposition at pH 3.0 was examined using conventional electrochemical techniques: cyclic voltammetry and impedance measurements (differential capacity-potential plots) and Surface-Enhanced Raman Spectroscopy (SERS), through a wide range of electrode potentials. The spectroelectrochemical results indicate that the electroactive species for silver electrodeposition are Ag+ ions and [Ag(Pic)] complexes, in spite of the predominant species in solution being the zwitterion (HPic). Adsorption of the anion (Pic-) occurs through a wide potential range where the electrode surface charge density is positive. However, HPic deprotonation, hydrogen formation and Pic- desorption, with the consequent decrease in SERS intensity, occur at the zero-charge potential (pzc) for HOPG.