Study on carbon nanotubes and activated carbon hybrids by pyrolysis of coal

Carbon nanotubes (CNTs) and activated carbon (AC) hybrids were obtained by co-pyrolysis of potassium hydroxide and bituminous coal. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Raman spectroscopy, X-ray Diffraction (XRD), and nitrogen adsorption measurements were used to investigate the characteristics of the samples and the effects of the final pyrolysis temperature and time on the structure of the carbon materials. The results indicated that the optimal range for the pyrolysis temperature and time for CNT growth were 900–950 °C and 45–90 min, respectively. The diameters of the as-prepared CNTs were in the range of 50–250 nm and their lengths were ∼15 μm. During the pyrolysis process, potassium hydroxide not only acted as the catalytic precursor to catalyze the CNT growth but also reacted with carbon to produce abundant micropores. Furthermore, the content of CNTs in the product after demineralization was significantly reduced. It was further confirmed by Inductively Coupled Plasma (ICP) analysis that the content of Fe, Co, and Ni decreased after demineralization, indicating that minerals in coal play an important role in the growth of coal-based CNTs.