Effects of carbon nanotube on the nucleation and growth of CO2 hydrate: Insights from the molecular dynamics simulations

•A small number of carbon nanotubes had little effect on the formation of hydrate.•When the carbon nanotubes were abundant, multiple carbon nanotubes appeared to agglomerate due to hydrophobicity.•Only when the number of carbon nanotubes is appropriate can carbon nanotubes effectively promote the nucleation and growth of hydrate.•The length of carbon nanotubes plays an essential role in the stable growth of the hydrate cages.