Shape-controlled electrodeposition of single Pt nanocrystals onto carbon nanoelectrodes.

In this paper, we report the electrosynthesis and characterization of individual, shape-controlled Pt nanocrystals (NCs) electrodeposited on carbon nanoelectrodes (CNEs). Single Pt NCs were deposited onto the CNEs using an empirically developed square-wave potential program. Characterization by scanning electron microscopy indicates that the sizes of Pt NCs are remarkably reproducible (relative standard deviation = 6%). Electrochemically active surface areas, determined by Cu underpotential deposition and H adsorption/desorption analyses, are also reproducible. Selected area electron diffraction indicates that each Pt NC is comprised of just one single crystal (no grain boundaries). Although different square-wave potential programs lead to different types of crystals, the Pt NCs discussed here have a concave hexoctahedral geometry bound primarily by {13 6 2} surface facets. The results in this report represent a first step toward our ultimate goal of studying electrocatalysis at individual, shape-controlled, single-crystal nanoparticles.