Preparing Nitrogen-Doped Multiwalled Carbon Nanotubes with Regionally Controllable Heterojunction Structure by Nondestructive Postdoping with the Assistance of Heating Fluorination

Abstract

This paper presents a feasible and universal approach to fabricate regionally controllable nitrogen-heteroatom-doped multiwalled carbon nanotubes with a skin-core heterostructure (N-o-FMWCNT) with the assistance of defluorination in outer-layered fluorinated MWCNTs (o-FMWNCT). First, o-FMWCNT with outer fluorinated tubes encapsulating intact inner tubes was prepared through well-designed direct heating fluorination with temperatures from 25 to 180 °C. Subsequently, nitrogen-doping was implemented at a mild temperature under NH3 atmosphere (400 °C). According to the results of X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and elemental analysis, about 4.97 atom % nitrogen-heteroatom with primary pyridine-nitrogen configuration was successfully doped into the carbon skeleton at the outer tube of o-FMWCNT with the recombination of C–N bonds. Because of the integrity of its inner tubes, the N-o-FMWCNT was endowed with a relatively high-level conductivity (5.46 × 10–2 S·m–...