Catalytic growth of carbon nanotubes with large inner diameters

Carbon nanotubes(2.4g/g.cat) with large inner diameters are synthesized through pyrolysis of methane on a Ni-Cu-Al catalyst by adding sodium carbonate into the carbon nanotubes growth system.The inner diameter of carbon nanotubes prepared by this method is about 20 nm~60 nm,while their outer diameter is about 40 nm~80 nm.Transmission electron microscopy(TEM) and X-ray diffraction(XRD) are employed to investigate the morphology and microstructures of carbon nanotubes.The analyses show that these carbon nanotubes have large inner diameters and good graphitization.The addition of sodium carbonate into the reaction system brings about slight decreases in the methane conversions and the yield of carbon.Our experiments results show sodium carbonate is a mildly toxic material that influences the catalytic activity of the Ni-Cu-Al catalyst and results in the formation of the carbon nanotubes with large inner diameters.The growth mechanism of the carbon nanotubes with large inner diameters is discussed in this paper.