Synthesis of Platelet Carbon Nanofiber/Carbon Felt Composite on in Situ Generated Ni−Cu Nanoparticles

Abstract

A platelet carbon nanofiber/carbon felt composite with a high surface area (>250 m 2 /g) is synthesized over a carbon felt supported Ni-Cu catalyst using ethane-hydrogen mixtures at 923 K. A uniform layer of carbon nanofibers is thus achieved via an in situ generation and dispersion of Ni-Cu nanoparticles induced by the surface reaction of hydrocarbon decomposition. This represents a cost-effective and flexible method without the requirement for presynthesis of uniformly distributed nanoparticles. Both thermodynamic analysis and experimental observation reveal that, in the initial growth period, formation of a molten phase of the nanosized Ni-Cu-C phase promotes the fragmentation of Ni-Cu parent particles of micrometer size. A unique octopuslike growth mode is observed during the formation of graphene layers from this liquid-like Ni-Cu-C system. A comparative study between Ni and Ni-Cu catalysts is performed. It is found that the addition of Cu in the Ni-Cu catalysts can enhance the fragmentation ability of the parent Ni-Cu particles when contacting with hydrocarbon. A treelike growth mode of carbon nanofibers grown on Ni-Cu catalysts is observed due to the further fragmentation of Ni-Cu particles during carbon nanofiber growth. In contrast to Ni-Cu catalysts, two different growth mechanisms on the Ni catalyst are found: a governing tip-growth mechanism by particles smaller than 50 nm and an octopus-like growth mechanism by larger particles (50-100 nm). The graphene sheet orientation in the carbon nanofibers depends on the composition of the metal particle; fishbone carbon nanofibers are obtained with carbon felt supported Ni catalysts, while platelet carbon nanofibers were obtained with Ni-Cu catalysts. The formation of platelet carbon nanofibers from the Ni-Cu catalysts is ascribed to a higher degree of interface wetting between the Ni-Cu particle and the produced graphene sheets.

Catalytic Consequence of the Interface Between Iron Catalysts and Foils in Synthesis of Aligned Nanocarbons on Foils

“…It leads to fragmentations of the large particle to several small particles and subsequent CNTs growth. Such fragmentations of small particles from a large particle have also been observed for Ni-Cu catalysts in ethane/hydrogen mixture [54]. This might explain the SEM observation in Fig.…”

Nitrogen-doped carbon nanomaterials: To the mechanism of growth, electrical conductivity and application in catalysis

“…Along with this, the formation of surface metal carbide MeC x can be considered proven because it was verified by experimental studies using the microscopy and in situ XPS methods [28,36]. Dissolution of carbon in the metallic particle can covert it into molten phase since the dissolution of C in Me-C system can significantly decrease the melting temperature of this system [37,38].…”

Effect of Calcination Temperature on Cu-Modified Ni Catalysts Supported on Mesocellular Silica for Methane Decomposition

“… 45 , 46 For platelet CNF formation, the graphite platelets were stacked in a direction parallel to the base of the metal particle and perpendicular to the fiber axis via the tip-growth mechanism. 47 , 48 …”