Flame spray pyrolysis generated transition metal oxide nanoparticles as catalysts for the growth of carbon nanotubes

Abstract

Herein, we investigate the growth of multi-walled carbon nanotubes (CNT) using three transition metal oxide nanoparticles; namely hematite (Fe2O3), cobalt oxide (Co3O4) and nickel oxide (NiO). The nanoparticles were synthesised using flame spray pyrolysis (FSP). As the nanoparticle and CNT syntheses are identical for all materials, a direct comparison between the products is possible and a link between catalyst and morphology of the resultant nanostructures can be elucidated. Conventional CNT were grown on Fe2O3 nanoparticles, no discernible nanotubes were observed on the Co3O4 catalysts whilst a mixture of conventional and coiled CNT (CCNT) were synthesised on the NiO nanoparticles. We investigated the effect of temperature, time and acetylene/hydrogen gas mixtures on the morphology, yield and purity of the CNT produced. By regulating the acetylene pyrolysis temperature for NiO, the CCNT yield can be increased to approximately 70% of the CNT yield.