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

• High yield and quality SWCNT growth was achieved on Co-Mo/MgO catalyst synthesized by gel-combustion method.
• For both high quality and high yield CNT growth it was necessary to use H2 in both catalyst pretreatment and growth processes.
• CNT yield was generally inversely proportional to the H2 flow rate, however, CNT quality increased with increasing H2 flow rate.
• Using Ar increased CNT yield, but obtained CNTs were mostly MWCNT and more defects were observed.
• The highest SWCNT yield of 1526% was obtained at a growth temperature of 950 °C at 200 sccm H2 flow rate.

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 H2 flow rates. It was observed that CNT yield decreased with the H2 flow rate, however, quality increased with increasing H2 flow rate. CNT yield increased for the temperatures 850–950 °C but dropped significantly above 950 °C. In this study, the highest yield of 1526% was obtained at the growth temperature of 950 °C. The optimum H2 flow rate was 200 sccm; this rate gave both high graphitization and high yield of product. Various CNT growth atmospheres including Ar, H2 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 H2. 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 statementWe 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%.

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