In situ regeneration of clean and ordered Pd(111) electrode surfaces by oxidative chemisorption and reductive desorption of iodine

Abstract

The single-crystallinity of a Pd(111) electrode surface which has been subjected to electrochemical oxidation is not restored when the oxided surface is reduced back to the metal. Interfacial order can be re-established if the disordered surface is immersed at ambient temperatures in aqueous iodide. Application of sufficiently negative potentials leads to reductive desorption of the chemisorbed iodine to regenerate a clean and well-ordered Pd(111) surface. An Ar +-ion-bombarded Pd(111) surface can also be re-ordered by multiple sequences of electrochemical surface oxidation and reduction followed by several cycles of oxidative chemisorption and reductive desorption of iodine. The experiments were performed at pH 10 in order to prevent the dissolution of Pd surface layers and show that the re-ordering process is driven predominantly by the strong chemisorption of iodine. The present results constitute the first demonstration of a method, performed completely under electrochemical reaction conditions, for the regeneration of a clean and ordered noble-metal single-crystal surface.