Low-temperature growth of bamboo-like multi-walled carbon nanotubes over an atomic layer epitaxy-Cu/SiO₂ catalyst via metal-support interaction

The well-controlled growth of carbon nanotubes (CNTs) at low temperature (< 1073 K) using non-iron group metal catalysts remains a challenge. Here, we report that CNTs can be grown at 773-1173 K over an atomic layer epitaxy (ALE) prepared copper catalyst (ALE-Cu/SiO₂) using chemical vapour deposition in helium diluted ethylene. At the same reaction conditions, only amorphous carbon can be generated over an impregnation (IM) method prepared copper catalyst (IM-Cu/SiO₂). A metal-support interaction (MSI) model is proposed to describe the interaction between the ALE prepared Cu nanoparticles (NPs) and SiO₂ support through the results of temperature programmed reduction profiles, X-ray photoelectron spectra and in situ X-ray diffraction (XRD) patterns. Structurally stabilised CuNPs in ALE-Cu/SiO₂ catalyst indicate that the strong MSI site of CuNPs and/or copper silicide (Cu₃Si) evidenced by in situ XRD patterns would be the active centers to fabricate CNTs. Our observations provide new insights into controlling the CNT growth at low-temperatures over non-ferromagnetic catalysts.