Aligned N-Doped Carbon Nanotube Bundles Prepared via CVD Using Zeolite Substrates

We report the synthesis of aligned N-doped carbon nanotube bundles via CVD (over the temperature range 700−800 °C) using ammonium-exchanged zeolite-β as the substrate, ferric nitrate as the catalyst, and acetonitrile as the carbon precursor. Ammonium exchange of the zeolite was found to be necessary for the formation of aligned N-doped carbon nanotubes (CNTs). The optimal temperature for the production of large amounts of aligned N-doped CNTs was found to be 750−800 °C. The N-doped CNTs had nitrogen content of between 6 and 9 wt %. The aligned CNTs grew in bundles along the verges, perpendicular to the surface of the hexagonal zeolite-β particles, and retained their aligned order after removal of the zeolite substrate. The length of the CNTs was in the range 2−10 μm depending on CVD temperature, with inner and outer diameters of ca. 10 and 30 nm, respectively. The CNTs exhibited high levels of graphitic ordering and thermal stability in air and had relatively high surface area (226−886 m2/g) and pore volume (0.3−0.81 cm3/g). The aligned N-doped CNTs had a bamboolike morphology with transverse carbon bridges forming compartments.