Catalytic behavior of noble metal nanoparticles for the hydrogenation and oxidation of multiwalled carbon nanotubes.

The catalytic behavior of various noble metal nanoparticles (NPs) supported directly on multiwalled carbon nanotubes (MWCNTs) was observed using environmental transmission electron microscopy (E-TEM). Gasification of the MWCNTs via catalytic hydrogenation or oxidation progressed at ∼450°C in conjunction with certain noble metal NP catalysts at the interface between MWCNTs and the NPs. During such catalytic reactions, the NPs were observed to move rapidly over the MWCNT surfaces. The mobility and wettability of the NPs varied depending on the particular metal NPs employed and the ambient atmosphere. While rhodium NPs exhibited high wettability under both hydrogen and oxygen atmospheres, the wettability of platinum, palladium and iridium NPs on MWCNTs varied with the atmosphere. The metal NPs seemed to have high degrees of crystallinity while their morphologies fluctuated throughout the catalytic reactions.