Efficient synthesis of aligned nitrogen-doped carbon nanotubes in a fluidized-bed reactor

Vertically aligned nitrogen-doped carbon nanotubes (NCNTs) with uniform size distribution, large aspect ratio, good orientation, and high purity were employed as novel platforms to understand the dopant-induced perturbations and found widely applications in catalysis, electrochemistry, energy conversion and storages. However, the efficient way to synthesis CNTs with ordered alignment in large scale is still a challenge. We reported NCNTs were efficiently synthesized on a lamellar vermiculite catalyst in a fluidized-bed reactor. The catalysts and as-grown products can maintain good fluidization state during the whole growth process. The intercalated growth mode prevented the NCNT arrays from the disturbance of particle collisions in the fluidized bed. With the introduction of nitrogen precursor, N atoms were doped into CNTs and formed NCNTs with bamboo-like structure. The content of N doping can be tuned in a range of 1.55-4.23% and the distribution of N-containing functional groups can also be modified by changing either the growth temperatures or nitrogen sources (NH ₃, 1,2-ethylenediamine, and pyridine). We explored the growth temperature ranging from 650 to 800 °C. High growth temperature led to a high NCNT yield (2.95 g _NCNT/g _cat h), large NCNT diameter (about 20 nm), and high graphitization degree. This provides a potential way for the controllable mass production of aligned NCNTs for applications in catalysis, materials science, energy conversion and storage, etc.