Multiple Alkynes React with Ethylene To Enhance Carbon Nanotube Synthesis, Suggesting a Polymerization-like Formation Mechanism

• DOI: 10.1021/nn101842g
• Publication Date: 2010-11-04T19:42:49Z
• Authors: Desirée L. Plata; Eric R. Meshot; Christopher M. Reddy; A. John Hart; Philip M. Gschwend
• Keywords: Acetylene; Alkyne; Carbon fibers

Thermal treatments of feedstock gases (e.g., C2H4/H2) used during carbon nanotube (CNT) synthesis result in the formation a complex mixture volatile organic compounds and polycyclic aromatic hydrocarbons. Some these are likely important CNT precursors, while others superfluous possibly degrade product quality, form amorphous carbon, and/or contribute to growth termination. To simulate effect thermal treatment without this chemical complexity, we delivered trace amounts individual hydrocarbons, along with ethylene hydrogen, cold-wall atmospheric pressure reactor containing locally heated metal catalyst (Fe on Al2O3). Using compound-specific experiments, demonstrate that many alkynes acetylene, methyl vinyl acetylene) accelerate multiwalled system. Furthermore, is required for enhanced growth, suggesting alkyne may react concert at catalyst. This presents distinct mechanism where precursors be intact C−C bond formation, such as polymerization reactions, challenging widely accepted hypothesis completely dissociate into C (or C2) units before "precipitating" from metal. Armed mechanistic insights, were able high-purity CNTs rapidly 15-fold improvement yield, 50% reduction energetic costs, order magnitude unwanted byproduct toxic smog-forming chemicals greenhouse gases).