Identification of appropriate catalyst system for the growth of multi-walled carbon nanotubes via catalytic chemical vapor deposition process in a single step batch technique

Abstract

Large quantities of well-aligned and purified Carbon nanotubes (CNTs) are to be produced for commercial applications. For this purpose, the design of an efficient catalyst system is very essential, which should have high catalytic activity, stability, and high diffusion of carbon. In this investigation, an attempt has been made to find a possible catalyst system that supports high yield with a defect-less structure of CNTs. Catalytic chemical vapor deposition (CCVD) single step batch process was used to synthesize CNTs in a single experiment (run) using six different mono-metallic and bi-metallic catalysts (NiO, CoO, CuO, NiO/CuO, NiO/CoO, CoO/CoO) systems. The catalyst materials were synthesized by the impregnation method. The mono-metallic and bi-metallic catalyst particles were characterized by SEM, XRD, and TGA. The carbon products obtained from different catalysts compositions were analyzed using FESEM, HRTEM, and Raman spectroscopy. The yield percentage of multi-walled CNTs was calculated. The aerial density of the CNTs grown on different catalyst compositions was found using image J technique. The diameter distribution of both catalyst compositions and grown CNTs were evaluated using their respective SEM and FESEM images. From this investigation, it was found that NiO/CuO produced higher yield of CNTs with well-aligned structure. CuO/CoO catalyst system produced amorphous carbon. The bi-metallic catalyst compositions grow higher yield and well-aligned CNTs as compared to mono-metallic catalyst systems.