2 Dimensional Dendrites and 3 Dimensional Growth of Electrodeposited Platinum Nanoparticles

Abstract

Platinum (Pt) nanoparticles are of particular interest as catalysts or electrocatalysts in the electrochemical reduction of oxygen. The morphology of Pt nanoparticles is correlated to their catalytic activity. A mechanism for heteroepitaxial Pt particle dendrite formation (2D growth) and coalescence (3D growth) on highly ordered pyrolytic graphite (HOPG) was observed. The mechanism of 2D dendrite growth, which appeared to be the dominant mechanism at low ionic concentration, was similar to colloidal aggregation, while 3D growth occurred at a high ionic concentration. With increasing number of Pt atoms in a cluster, the simulated interaction energy between the Pt cluster and HOPG substrate decreases. The DLVO theory gives some insight into two different growth mechanisms. The energy barrier between coalescing particles decreases with increasing concentration of electrolytes. Various morphologies of Pt electrodeposition on HOPG were suggested based on the competition between 3D growth and 2D particle growth.