Synthesis of Carbon Nanotubes using Catalytic Chemical Vapour Decomposition of Acetylene over Co-Mo bimetallic Catalyst supported on Magnesia

Abstract

This research work investigates the utilization of acetylene as a precursor for the synthesis of multiwalled carbon nanotubes (CNTs) over bimetallic Co-Mo catalyst supported on magnesia (MgO) via catalytic chemical vapour deposition (CCVD) technique. The CCVD equipment requires the use of catalyst and support in addition to a carbon source (acetylene) and nitrogen gas for CNTs growth. The bimetallic Co-Mo catalyst supported on MgO was prepared by the wet impregnation method, which was placed in the quartz boot inside the CVD equipment. The catalyst sample with the highest yield of 93.22 % was prepared from 16 g support mass, stirring speed of 1500 rpm, stirring time of 20 minutes, drying temperature of 120℃ and drying time of 10 hours. The catalyst was characterized using high-resolution scanning electron microscopy (HRSEM) and X-Ray diffraction spectroscopy (XRD) to determine the catalyst crystallinity, morphology and elemental composition. The catalyst developed was utilized for the synthesis of CNTs by chemical vapour deposition method (CVD) with acetylene as the carbon source and nitrogen as the carrier gas while the CVD furnace was programmed to heat at 10℃ per minute. The effects of synthesis parameters (calcination temperatures, reaction time, and gasses flow rates) on the yield of the CNTs were examined with 24 factorial experimental design. The highest yield of 89.09 % of CNTs was obtained at a temperature of 700℃, 250 mL/min and 200 mL/min flow rate for acetylene and nitrogen, respectively. The XRD patterns of the as-synthesized CNTs revealed the development of graphitized carbon, the high-resolution scanning electron microscopy (HRSEM) micrographs indicated the formation of fairly uniform and evenly dispersed carbon nanotubes were grown on the support, while the high-resolution transmission electron microscope (HRTEM) confirm the formation of CNTs with a particle size between 31.21 and 45.03 nm. Also, the HRTEM results further revealed the increase in diameter of CNTs when the temperature is raised from 700℃-800℃. This study establishes the production of CNTs from acetylene precursor over bimetallic Co-Mo catalyst supported on MgO in a CVD reactor.