On the electrocatalysis of nanostructures

ELISABETH SANTOS; PAOLA QUAINO

Krakow

Simposio; 2nd International Symposium on Surface Imaging/Spectroscopy at the Solid/Liquid Interface; 2009

In the perpetual search for better catalysts, electrochemists have turned to various metal nanostructures in recent years. Indeed, electrochemistry offers convenient means to generate various nanostructures such as metal overlayers, steps decorated by adatoms, or even monoatomic nanowires. The big scientific challenge is to understand, how the structure affects the chemical and physical properties of the materials, and how this in turn influences their reactivity. In this work, we want to make a contribution to this problem and examine a few structures involving catalysts, on which much attention has been focused recently: submonolayers, monolayers and clusters of platinum and palladium on different substrates. The physical and electronic properties of these nanostructures have been investigated by density functional calculations performed with the dacapo code. In the present work, we use the SKS formalism and the Hückel theory to describe the bonding of the molecule and DFT to obtain the d band structures of the nanostructures.RESULTSAs an example, we analise the density of states of the d band (DOS) for two differentstructures of cluster of Pd on Au(111) and the corresponding adiabatic potential energy surface for the oxidation of hydrogen. A Pd cluster adsorbed on the surface is more favorable than the embedded cluster for the oxidation of hydrogen. Important changes are observed in the DOS of the d band of Pd and in the electrocatalytic properties. On the basis of these early results, we can predict, which of these structures are the best catalysts for hydrogen evolution or oxidation. Experimental data confirm these results.