Nanopore structure of highly enriched double-walled carbon nanotube network assemblies

An efficient catalytic chemical vapor deposition method utilizing an Fe-Mo/MgO-supported catalyst was developed, allowing the highly selective synthesis of double-walled carbon nanotubes (DWCNTs) in high yield, exceeding 89 %. The carbon yield, tube diameter, and crystallinity of the synthesized DWCNTs were characterized using high-resolution transmission electron microscopy, field-emission scanning electron microscopy, thermogravimetric analysis, and Raman spectroscopy. The nanopore structure and adsorption characteristics of the DWCNTs purified by removing the support and catalyst (i.e., Fe-Mo/MgO) were analyzed via N₂ adsorption–desorption measurements at 77 K. A remarkable advantage of the highly enriched DWCNTs with small bundle network structures is that guest molecules can easily access the outer (i.e., external) surface of the DWCNTs, resulting in a large specific surface area (SSA) of >691 m² g⁻¹ and pore volume of 2.70 mL g⁻¹ in the double-walled structures. Thus, highly enriched DWCNTs with large pore volumes and SSAs prepared via facile solution-based processes can yield CNT-based structures for applications in high-performance energy storage.