High-precision synthesis and electrochemistry of Pt nanoparticles

Abstract

The effect of catalyst particle size on electrochemical reactions remains underestimated. In the process of developing new nanoscale catalysts, it is critical to study monodisperse specimens with strict control over particle diameter and morphology in order to distinguish the particle size effect from other experimental variables. Here, we report a new method for size-controlled Pt nanoparticle synthesis by separating the homogeneous nucleation and heterogeneous growth steps. Using this approach, monodisperse Pt nanoparticles were synthesized with diameters of 3, 5, and 7 nm (σ < 10%). Electrochemical evaluations show size-dependent adsorption–desorption behavior at the catalyst–electrolyte interface, indirectly revealing the surface morphology. Platinum nanoparticles with a 5 nm diameter are confirmed to have an optimal balance between activity for the oxygen reduction reaction (ORR) and dissolution, due to a desirable ratio between surface atoms with low-coordinated vertex and edge sites and surface facets with higher coordination.