Growth of Graphite Nanofibers from the Iron−Copper Catalyzed Decomposition of CO/H2Mixtures

Abstract

We have investigated the formation of graphite nanofibers from the catalytic decomposition of CO/H 2 mixtures over a series of powdered Fe-Cu catalysts at temperatures ranging from 500 to 700 °C. The physical and structural characteristics of the nanofibers have been established from examination of the materials by a variety of techniques including transmission electron microscopy, temperature-programmed oxidation, nitrogen surface area measurements, and X-ray diffraction. It was found that the addition of Cu to Fe did not exert a significant influence on the amount of solid carbon product formed in the reaction. On the other hand, examination of the nanofibers by high-resolution TEM revealed that the materials generated from Fe-rich Cu bimetallics were notably more graphitic in nature than those grown from pure Fe. As the reaction temperature was increased from 600 to 700 °C, the structure of the graphite nanofibers underwent a dramatic change from a platelet to tubular configuration. It is suggested that this transformation is directly associated with the α-Fe to γ-Fe phase change over this temperature range.