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

M. FONTICELLI; G. CORTHEY; A. FLORIDIA ADDATO; ALDO A. RUBERT; G. BENITEZ; R. C. SALVAREZZA

Niza

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

The platinum group metals (PGMs) have outstanding catalytic properties. They have been widely applied in chemical, petrochemical, pharmaceutical, electronic, and automotive industries. Among them, both Pd and Pt possess distinctive ability in catalyzing partial oxidation, hydrogenation and dehydrogenation of a variety of important molecules that are essential in many industrial processes. Although carbonsupported PGMs -or their alloys- catalysts can be produced by the widely used impregnation approach, such catalysts typically do not have the uniformity in size, shape and composition among individual particles in comparison to those made by colloidal or micro emulsion methods. In this regard, thiolates have demonstrated to be the most versatile family of capping agents for the synthesis of ligand-stabilized metallic and semiconductor nanoparticles. However, the current knowledge with regards 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 and curved (nanoparticles) Pt and Pd surfaces was studied by electrochemical techniques and X-ray photoelectron spectroscopy (XPS). With regards to the chemical nature of adsorbates, thiolate-SAMs on Pt resemble those grown on Ag and Au. On the other hand, alkanethiols adsorbed on Pd surfaces lead to a complex interface composed of thiolate and sulphide[1], which is possibly responsible for its high stability[2]. In the case of Pt, the SAMs start to be desorbed in the hydrogen adsorption region, which makes the electrochemical desorption at negative potentials a suitable alternative for nanoparticle’s cleaning. Therefore, it has been considered the role that hydrogen may play in the SAMs’ desorption. It is analyzed whether the ability to adsorb H can be correlated with the stability of the SAMs on these metals. [1] Love, J. et. al. J. Am. Chem Soc. 125 (2003) 2597. [2] Corthey, G. et. al J. Phys. Chem. C. 113 (2009) 6735.