Oxygen Defect Engineering toward the Length-Selective Tailoring of Carbon Nanotubes via a Two-Step Electrochemical Strategy

Abstract

A systematic study shows that carbon nanotubes (CNTs) with tunable lengths can be obtained by a simple two-step electrochemical approach via oxygen defect engineering. The preoxidation of CNTs in the H2SO4 electrolyte controllably introduces oxygen defects onto the sp2-hybrid carbon skeleton. This is the key to high-efficiency tailoring of the CNTs with different length distributions (i.e., ∼640, ∼308, and ∼130 nm) by the following oxidation in NaOH electrolyte. In addition, the short-cut CNTs are free of metal impurities and destructive damage to their tubular structures, displaying excellent dispersibility in various solvents. This nondestructive cutting and purification strategy is a low-cost robust pathway to the scalable manufacturing of length-selective CNTs for various practical applications.

Cutting Methods and Perspectives of Carbon Nanotubes

“…Chemical methods are the most commonly used methods to shorten the length of CNTs. ,− Essentially, it is using oxidizing chemicals (like chemical scissors) to break the carbon bond. This method can deal with CNTs on a large scale and is easy to operate.…”

“…The commonly used physical/chemical cutting methods mainly include the ultrasonic/acid oxidation method, photocatalytic method, electron beam/nickel method, and electrochemical method. ,,,,− In essence, the ultrasonic/acid oxidation method is to destroy the carbon bonds with oxidizing chemicals and then break the CNTs with ultrasonication. This method can also be applied to the large-scale treatment of CNTs, and the operation is simple.…”

“…The electrochemical cutting of CNTs usually refers to the electrochemical oxidation of CNTs (to introduce oxygen-containing defects) or the destruction of sp 2 carbon bonds by the electric field. Zhang et al designed a two-step electrochemical method to explore the cutting of CNTs with oxygen defects . The cutting process is divided into two steps: the first step is to put the pristine carbon nanotubes (P-CNTs) in the H 2 SO 4 solution with different charges to prepare CNTs with oxygen defects; the second step is to put the CNTs with oxygen defects into the NaOH solution for electrochemical oxidation cutting (Figure a).…”

Introducing Electrochemically Active Oxygen Species to Boost the Pseudocapacitance of Carbon‐based Supercapacitor

“…During the anodic polarization process, the carbon electrode would be in-situ oxidized through direct oxidation by electrophilic substitution reactions [26] and/or indirect oxidation by in-situ generated oxygen intermediates [27][28][29] (like hydroxyl radical), without the utilization of extra oxidant or vigorous conditions. Since the electrochemical oxidation reaction only occurs on the conductive carbon skeleton, the introduced oxygen species can uniformly bond with the conductive carbon substrates, which strengthens the stability and ensures the electrochemical activity.…”

Role of Defect Engineering and Surface Functionalization in the Design of Carbon Nanotube-Based Nitrogen Oxide Sensors

“…For instance, these exhibit fascinating properties, such as superior electrical conductivity [ 17 , 18 ], large surface area [ 19 ], excellent mechanical flexibility [ 20 ], high thermal/chemical stability [ 21 , 22 ], and high electron mobility [ 23 ]. Although pristine CNTs have shown promising performance for NOx detection [ 24 , 25 , 26 ], several strategies have been developed such as surface functionalization and defect engineering to improve the NOx sensing of pristine CNT-based sensors [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. Through these strategies, the sensing properties of modified CNTs toward NO x gases have been substantially improved [ 38 , 39 , 40 ].…”