Holey Carbon Nanotubes from Controlled Air Oxidation

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, is 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 leads to unique advantages, such as bandgap widening, chemical functionalization of hole edges, and improved accessible surface area. Here, a facile and scalable method to prepare holey carbon nanotubes via controlled air oxidation is presented. Although no additional catalyst is added, the residual iron nanocatalysts encapsulated in the nanotube cavity from nanotube manufacturing significantly contributed to the hole generation through the nanotube walls. The holey carbon nanotube products exhibit enhanced surface area, pore volume, and oxygen‐containing functional groups, which lead to their much enhanced electrochemical capacitive properties (increased over 100% in capacitance). Synthesis and characterization details of this novel class of holey carbon nanomaterials are presented, and their potential applications are discussed.