Meso-channel development in graphitic carbon nanofibers with various structures

A general method based on oxidation and heat expansion was developed to introduce mesoporous channels into the catalytically grown carbon nanofibers (CNFs) with platelet, herringbone, and tubular structures. Strong oxidation of CNFs caused large amounts of oxygen functionalities to be intercalated in the c-plane of the graphene layers, increasing the interlayer spacing. These intercalated components vaporized rapidly during the heat treatment, forcing apart adjacent graphene sheets and, thus, forming mesoporous channels. The obtained mesoporous CNFs maintained the fibrous form and the graphene layer alignment of their parent CNFs, but they developed aligned mesoporous channels. These channels reflected the intrinsic structure of the CNFs, which would be further adjusted by changing the oxidation degree of the CNFs or the initial crystalline structure of the CNFs. The development of mesoporous channels increased remarkably the external surface area of CNFs. It has further been demonstrated that these mesoporous CNF supported Pt nanoparticles exhibited fairly high electrocalaytic activity for methanol oxidation. As a result of their large external surface area and good crystalline structure, these mesoporous CNFs should be excellent supports for the electrodes of direct methanol fuel cells.