ELECTROCHEMICAL-BEHAVIOR OF THE PT (111)-AS SYSTEM IN ACIDIC MEDIUM - ADSORBED HYDROGEN AND HYDROGEN REACTION

A detailed study of the deposition of arsenic on a platinum (111) oriented substrate was carried out by using either the technique of irreversible adsorption and transfer to 0.5 M H2St4 as the test electrolyte or classical UPD conditions. The relations between the two methods of layer formation were investigated. Adsorbed hydrogen was used to determine the stoichiometry of the arsenic surface compound formed and the hydrogen reaction for checking how compact the arsenic layer is. From this study it follows that classical adsorbed hydrogen cannot be considered as an intermediate in the hydrogen reaction. A discussion follows concerning the position of the arsenic adatoms relative to the atoms of the substrate as a consequence of the absence of a correlation between the underpotentially adsorbed hydrogen and the hydrogen reaction. © 1990.