Synergism of C₅N six-membered ring and vapor-liquid-solid growth of CN_x nanotubes with pyridine precursor

A series of bamboo-like CN_x nanotubes have been synthesized from pyridine precursor by chemical vapor deposition with bimetallic Fe-Co/γ-Al₂O₃ catalyst in the range of 550∼950°C. An unusual predomination of pyridinic nitrogen over graphitic nitrogen has been observed for the CN_x nanotubes with reaction temperature below 750°C. The pyridinic nitrogen decreases and the graphitic nitrogen increases with rising reaction temperature. A synergism mechanism of C₅N-six-membered-ring-based growth through surface diffusion and vapor-liquid-solid growth through bulk diffusion was accordingly deduced and schematically presented. This mechanism could not only explain our own experimental results, but also understand the CN _x-nanotube-related experimental phenomena in the literature, as well as be in accordance with the basic principle of diffusion kinetics. A promising route to the challenging topic for synthesizing regularly arranged C ₅N or high-N-content CN_x nanotubes has also been suggested.