Holey Carbon Nanotubes from Controlled Air Oxidation

Abstract

Defects in various nanomaterials are often desirable to enable enhanced functional group attachments and attain properties that are not available with their intact counterparts. A new paradigm in the defective low-dimensional carbon nanomaterials is to create holes on the graphitic surfaces via partial etching. For example, holey graphene, graphene sheets with through-thickness holes, was synthesized using several different partial etching approaches and found useful for various applications such as field-effect transistors, sensors, energy storage devices, and separation membranes. In these applications, the presence of holes led to unique advantages, such as bandgap widening, chemical functionalization of hole edges, improved through-the-thickness ion transport with lowered tortuosity, and improved accessible surface area. Here, we present a facile method to prepare holey carbon nanotubes via controlled air oxidation. Although no additional catalyst was added, the residual iron nanoparticles from nanotube growth encapsulated in the nanotube cavity significantly contributed to the hole generation through the nanotube walls. The holey carbon nanotube products exhibited enhanced surface area, pore volume, and oxygen-containing functional groups, which led to their much enhanced electrochemical capacitive properties. Synthesis and characterization details of this novel class of holey carbon nanomaterials are presented, and their potential applications are discussed