Theoretical and experimental study for quantification of defects created by chlorine on nitrogen-doped carbon nanotubes

Abstract

Abstract Herein, we investigated the effect of chlorine addition into nitrogen solvents on the defect enhancement and morphology of carbon nanomaterials (CNMs). Tetrachloroethane and acetonitrile were used as sources of chlorine and nitrogen, respectively. Various morphologies were obtained by varying the amount of tetrachloroethane in the acetonitrile feed. Carbon nano-onions were dominating in CNMs generated from room temperature feed mixtures, which confirms that the materials were functionalized with chlorine and doped with nitrogen. Highly defective materials were generated from heated feed mixtures, as evidenced by the formation of branched bamboo-compartmented carbon nanotubes (CNTs), including other CNTs with morphologies such as nano-necklaces, coiled and broken bamboo-compartmented. Defects enhanced by the addition of tetrachloroethane and quantified using increased I D /I G peak intensity ratios obtained from Raman spectroscopy also confirmed enhanced deformation in heated feed mixtures. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that the types of defects present in these materials ranged from boundary-like, vacancy-like, hoping and on-site defects. The defected CNMs can be used as potential supports for metal or metal chalcogenides nanoparticle supports in electrochemical conversions. Theoretical calculations via density functional theory (DFT) revealed the appearance of a C–Cl peak at the CBM TDOS, which emanated due to the generation of an unoccupied mid-gap state originating from the sp 3 -hybridized defect brought by neutral chlorine adducts to the sp 3 -hybridized lattice of CNTs. A stronger interaction between C and N in N-doped CNTs and chlorinated N-doped CNTs was observed by an enhanced DOS and TDOS around the Fermi level previously assigned to π *.