Aligned CN_x nanotubes by pyrolysis of ferrocene/C₆₀ under NH₃ atmosphere

Aligned CN_x(x<0.1) nanotubes have been generated by pyrolyzing ferrocene/C₆₀ mixtures at 1050°C in an ammonia atmosphere. The structure and composition of the product were determined by high-resolution transmission electron microscopy and high spatial resolution electron energy-loss spectroscopy. The CN_x tubes (15-70 nm diameter, <50 μm length) grown in large flakes (<3 mm²) consist of a reduced number of "graphitic" layers (<15 on either side) arranged in a bamboo-like structure. Areas of high nitrogen concentration were found within curved or corrugated "graphite-like" domains. The observation of a well-developed double peak in the σ* feature of the N K-edge suggests that the material has not undergone the transition to the fullerene-like phase known for nitrogenated carbons. Incorporation of nitrogen from the gas phase (NH₃) into CN_x nanotubes therefore leads to improved and more efficient N substitution into the network as compared to the synthesis with solid nitrogen-containing precursors reported earlier.