Alkanethiols Adsorbed on Platinum and Palladium Surfaces: Composition and Stability Studies by Electrochemical Techniques and X-ray Photoelectron Spectroscopy

MARIANO H. FONTICELLI; GASTÓN CORTHEY; MARÍA ALEJANDRA FLORIDIA ADDATO; ALDO A. RUBERT; GUILLERMO A. BENITEZ; ROBERTO C. SALVAREZZA

Nice, France

Congreso; 61st Annual Meeting of international Society of Electrochemistry; 2010

international Society of Electrochemistry

The platinum group metals (PGMs) have outstanding catalytic properties. They havebeen widely applied in chemical, petrochemical, pharmaceutical, electronic, andautomotive industries. Among them, both Pd and Pt possess distinctive ability incatalyzing partial oxidation, hydrogenation and dehydrogenation of a variety ofimportant molecules that are essential in many industrial processes. Although carbonsupportedPGMs -or their alloys- catalysts can be produced by the widely usedimpregnation approach, such catalysts typically do not have the uniformity in size,shape and composition among individual particles in comparison to those made bycolloidal or micro emulsion methods. In this regard, thiolates have demonstrated to bethe most versatile family of capping agents for the synthesis of ligand-stabilizedmetallic and semiconductor nanoparticles. However, the current knowledge withregards to PGMs-thiolate interaction and thiolates self-assembled monolayers (SAMs)is poor in contrast to the vast literature of thiolates and their SAMs on gold and silver.In this work the stability and composition of alkanethiols adsorbed on planar andcurved (nanoparticles) Pt and Pd surfaces was studied by electrochemical techniquesand X-ray photoelectron spectroscopy (XPS). With regards to the chemical nature ofadsorbates, thiolate-SAMs on Pt resemble those grown on Ag and Au. On the otherhand, alkanethiols adsorbed on Pd surfaces lead to a complex interface composed ofthiolate and sulphide[1], which is possibly responsible for its high stability[2]. In thecase of Pt, the SAMs start to be desorbed in the hydrogen adsorption region, whichmakes the electrochemical desorption at negative potentials a suitable alternative fornanoparticle’s cleaning. Therefore, it has been considered the role that hydrogen mayplay in the SAMs’ desorption. It is analyzed whether the ability to adsorb H can becorrelated with the stability of the SAMs on these metals.