Chemical Vapor Deposition and Synthesis on Carbon Nanofibers:  Sintering of Ferrocene-Derived Supported Iron Nanoparticles and the Catalytic Growth of Secondary Carbon Nanofibers

Abstract

The synthesis of homogeneously distributed carbon nanofibers with well-defined morphology on vapor-grown carbon nanofibers was achieved by a sequence of gas-phase steps, thus fully avoiding wet chemistry: first, carbon nanofibers were exposed to oxygen plasma to introduce oxygen-containing functional groups. Then, the chemical vapor deposition of ferrocene was carried out under oxidizing conditions, yielding nanofiber-supported iron oxide nanoparticles.Secondary carbon nanofibers with diameters in the range from 10 to 20 nm were subsequently grown from cyclohexane catalyzed by the sintered metallic iron nanoparticles under reducing conditions. XPS was applied to monitor the chemical changes of the surface composition and the sintering of the metallic iron particles in hydrogen. The morphology and the height distribution of the sintered iron oxide nanoparticles was derived by a unique combined application of scanning electron microscopy and scanning tunneling microscopy. The specific surface area of the nanocomposite was enhanced strongly due to the growth of secondary nanofibers, and it was possible to tune the morphology of the nanofiber-nanofiber composites by the process parameters. Thus, a significant advance in the reproducible synthesis of branched carbon fiber nanocomposites was achieved.

Surface characterization and functionalization of carbon nanofibers

“…58 The specific surface area of the nanocomposite was enhanced by the growth of secondary nanofibers, and it was possible to tune the morphology of the nanofibernanofiber composites by the process parameters. First, CNFs were exposed to oxygen plasma to introduce oxygencontaining functional groups.…”

CNT-TiO2−δ Composites for Improved Co-Catalyst Dispersion and Stabilized Photocatalytic Hydrogen Production

“…Although the length of CNTs in CNT-TiO2−δ-60 is significantly greater than that in CNT-TiO2−δ-15, due to a longer growth time, all of the observed CNTs have a diameter of around 40-50 nm and were homogeneously grown on the surface of the TiO2−δ particles. It is supposed that the TiO2 particles are also bridged by CNTs in the micro-scale range [25], because uniformly distributed Fe nanoparticles (indicated by the absence of clear FeOx reflections in the XRD pattern of CVD-synthesized FeOx/TiO2 catalyst in Figure S3) serving as the catalyst for CNT growth form on the surface of TiO2 [21,26]. As a consequence, a different performance from that of TiO2 and TiO2−δ can be expected for the CNT-TiO2−δ composites in photocatalysis.…”

Support Materials and Characterization Tools for Nanostructured Catalysts

“…In particular we note the work of the group of Su and Schlögl [10][11][12], the group of Muhler [13,14] and the group of Lefferts [15]. Hereafter we present case studies of the use of carbon nanofiber (CNF) support material for fundamental research in catalysis.…”