Controlled electrochemical decoration of metal nanoparticles: Theoretical considerations and computer simulations

EZEQUIEL PEDRO M LEIVA

San Antonio

Encuentro; First Meeting of the American Initiative on Metal Clusters and Nanoalloys; 2011

UTSA

The singular properties of metallic nanoparticles(NP) have awaked great interest in both the scientific and technological communities, and the size-dependence of their thermodynamic properties has been a hot topic of research in recent years. Currently, there are several methods to control the size of metallic NP. In those cases where NP growth is controlled by a redox system, the chemical identity of the redox species and/or the concentration ratio between the surfactant and the precursor agent [1] constitute the main variables. While extensive experimental effort has been devoted to understand this phenomenon, there are very few examples on theoretical modeling available to unveil the role played by each of these variables on the final size of the NP. On the general context, our talk will discuss on the feasibility of the extension of a phenomenon denominated underpotential deposition(upd) in electrochemistry to metallic NP. In the case of planar electrodes, upd refers to the deposition of one or two monolayers of a metal on a foreign substrate at potentials more positive than that predicted by Nernst equation, in apparent violation to thermodynamics. In the past, we have modeled this phenomenon for planar surfaces in several approaches, involving first-principles calculations, molecular dynamics and Monte Carlo simulations. In the present talk, we introduce a statistical mechanical model [2-4] aimed to describe this phenomenon for nanoparticles. The model describes the role played by each of the following variables : nature and activity of the substrate and reactants, the size, shape and metallic nature of the NP, and the effect of the super and undersaturation conditions. A brief discussion on the model will be made illustrating its application with computer simulation using realistic interatomic potentials. The thermodynamic stability of different structures like Au/Ag, Pd/Au, and Pt/Au will be presented, and possible experiments to test the model will be proposed.