Catalyst regeneration and multicycle growth of high purity and yield semiconducting single-walled carbon nanotubes

Abstract

Single-walled carbon nanotubes (SWCNTs) with specific electrical types are urgently demanded for future nanoelectronic applications. However, it is still a challenge to simultaneously improve the purity and yield of semiconducting SWCNTs (s-SWCNTs). Herein, we propose a new multicycle approach to directly synthesize s-SWCNTs by chemical vapor deposition (CVD) using Fe0.01Mg0.99O as catalyst regeneration host. The appropriate carbon feedstock used in the first-time growth is CH4. During this process, the lattice oxygen would be released from Fe0.01Mg0.99O catalyst through H2 reduction and then form water vapor. The water vapor could in-situ selectively etch metallic SWCNTs (m-SWCNTs) in the nucleation process. After the termination of the first-time growth stage, the deactivative catalyst was regenerated by oxidation treatment, then it was reused to grow SWCNTs again. Carbon feedstock was changed to C2H5OH for the multicycle growth of SWCNTs and the secondary etching of as-grown m-SWCNTs and smaller-diameter SWCNTs. The selective synthesis of s-SWCNTs through this new multicycle growth process was up to 93.2% abundance, and the yield of SWCNTs was improved from 0.76% to 1.34% (weight ratio to the catalyst powder). It is interesting that there exists a diameter threshold value, which could affect the ∙OH groups etching on m-SWCNTs. According to the DFT simulation, the experimental results are related to the absorption capacity and reaction activity of SWCNTs. It presents a new approach to the massive synthesis of high purity s-SWCNTs and has wide applications in the future.