Hydrogen-induced Ostwald ripening of cobalt nanoparticles on carbon nanotubes

Nanoparticles on carbon nanotubes can be used as a high surface area catalyst or as a means to produce well-defined particles. In this study, cobalt nanoparticles were formed on xxsingle-walled carbon nanotubes during hydrogen exposure at an elevated temperature. The average particle size increased as a function of reaction time ranging from 1.5 to 40 nm, indicating hydrogen-induced Ostwald ripening which is remarkable for a nonhydrogen-absorbing material. Mass abundances and cobalt shells were observed which possibly contained hydrogen. The combination of large surface area, high atomic mobility, and hydrogen-induced Ostwald ripening resulted in a novel method to prepare various cobalt nanoparticle shapes and sizes.