Xiao Bo, Yu Xue-fang, Ding Yi-hong
State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, People's Republic of China.
J Mol Model. 2014 Mar;20(3):2125. doi: 10.1007/s00894-014-2125-8. Epub 2014 Feb 19.
Experimental studies have shown that chemical vapor decomposition method by using C₂H₂/C₂H₄ as carbon source could dramatically decrease the defects in prepared CNT. However, the inherent mechanism with regards to reduction of defects is quite unclear. In the present paper, density functional theory is used to study the healing process of CNT with divacancy defect by C₂H₂/C₂H₄ molecule. The healing processes undergo three evolution steps: (i) the chemisorption of the first C₂H₂/C₂H₄ molecule on defective CNT; (ii) the insertion of C atoms from C₂H₂/C₂H₄ molecule into defective CNT; (iii) the removal of the H atoms on CNT, forming perfect CNT. The estimated adsorption energy barrier of C₂H₂/C₂H₄ molecules on defective CNT is within the range from 1.10 to 1.63 eV, and the eventual formation of CNT is strongly exothermic (4.40/4.54 eV in (8, 0) CNT). In light of the unique conditions of CNT synthesis, i.e., high temperature in a closed container, such healing processes could most likely take place. Therefore, we propose that during CNT synthesis procedures, both C₂H₂ and C₂H₄ could act as a carbon source and the defect healer.
实验研究表明，以C₂H₂/C₂H₄作为碳源的化学气相分解法能够显著减少制备的碳纳米管中的缺陷。然而，关于缺陷减少的内在机制尚不清楚。在本文中，采用密度泛函理论研究了C₂H₂/C₂H₄分子对具有双空位缺陷的碳纳米管的修复过程。修复过程经历三个演化步骤：（i）第一个C₂H₂/C₂H₄分子在有缺陷的碳纳米管上的化学吸附；（ii）C₂H₂/C₂H₄分子中的C原子插入有缺陷的碳纳米管；（iii）碳纳米管上H原子的去除，形成完美的碳纳米管。C₂H₂/C₂H₄分子在有缺陷的碳纳米管上的估计吸附能垒在1.10至1.63 eV范围内，最终形成碳纳米管是强烈放热的（在(8, 0)碳纳米管中为4.40/4.54 eV）。鉴于碳纳米管合成的独特条件，即在密闭容器中的高温，这种修复过程很可能发生。因此，我们提出在碳纳米管合成过程中，C₂H₂和C₂H₄都可以作为碳源和缺陷修复剂。
