Adsorption Behavior of Pyridinecarboxylic Acids in Acidic Solution on a Polycrystalline Gold Electrode Surface Studied by Infrared Reflection Absorption Spectroscopy

Abstract

Adsorption behavior of three isomeric pyridinecarboxylic acids (picolinic acid: 2-PCA, nicotinic acid: 3-PCA, and isonicotinic acid: 4-PCA) in 0.1 M (M = mol dm-3) HClO4 solution on a smooth polycrystalline gold electrode surface was investigated by in situ infrared reflection absorption spectroscopy (IRAS). As the electrode potential became more positive, adsorbed 3- and 4-PCAs were found to reorient from a flat configuration to a vertical one that binds to the surface through lone pairs of electrons on two oxygen atoms of the carboxylate group. However, no significant adsorption of 2-PCA occurred on the electrode surface, and this finding indicates the ortho effect on adsorption.