The effects of catalyst pretreatment, growth atmosphere and temperature on carbon nanotube synthesis using Co-Mo/MgO catalyst

The growth of high quality and high yield carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CVD) of CH4 over Co-Mo/MgO catalyst was investigated for different growth temperatures and H-2 flow rates. It was observed that CNT yield decreased with the H-2 flow rate, however, quality increased with increasing H-2 flow rate. CNT yield increased for the temperatures 850-950 degrees C but dropped significantly above 950 degrees C. In this study, the highest yield of 1526% was obtained at the growth temperature of 950 degrees C. The optimum H-2 flow rate was 200 sccm; this rate gave both high graphitization and high yield of product. Various CNT growth atmospheres including Ar, H-2 and the mixture of both gases were also analyzed and it was observed that the highest quality CNTs were obtained for both pretreatment and growth carried out with H-2. This gave a high yield of 292%. On the other hand, CNT growth carried out under Ar atmosphere gave higher CNT yield of 368%, however, the CNTs grown with Ar were more defective and had larger diameters. Prime novelty statement: We demonstrate a sorbitol added catalysis synthesis method and importance of the ideal growth conditions to improve high quality single walled carbon nanotube yield up to 1500%. (C) 2015 Elsevier B.V. All rights reserved.