Catalytic oxidation of graphite by mass-selected ruthenium nanoparticles

The scanning tunneling microscopy and temperature programmed oxidation methods were used to study the catalytic oxidation of graphite by mass-selected Ru nanoparticles. Channeling by the nanoparticles was observed on the unsputtered HOPG basal surface at temperatures above 750 °C in 10−6 mbar O2O2. Ar+Ar+ ion bombardment was used to create layers of disordered carbon of various depths on the HOPG surface. The channel propagation rate in the disordered carbon layer was found to increase for larger nanoparticles. The depth of the interface between the disordered carbon layer and the graphite determined whether the nanoparticles etched paths parallel or perpendicular to the surface. The gasification onset temperature depended on the degree of graphitisation of the surface, with more heavily sputtered surfaces undergoing gasification at much lower temperatures than the unsputtered surface.

Ru nanoparticles act as catalysts for the oxidation of substrate carbon. The etch channels follow random paths when the nanoparticles etch disordered carbon but are highly directional when the nanoparticles are in contact with the graphite basal plane. The propagation rate increases with particle size.Figure optionsDownload as PowerPoint slideResearch highlights
► Size-selected Ru nanoparticles catalytically oxidise sputtered HOPG surfaces.
► Ru nanoparticles channel randomly through the disordered carbon layers.
► The nanoparticles become trapped at the graphite/disordered carbon interface.
► The onset temperature for the etching depends on how much the surface is pre-sputtered.
► The etch rate scales with the nanoparticle size.