Loops at Carbon Edges: Boron-Assisted Passivation and Tunable Surface Properties of Carbon Nanofibers

During thermal treatment of carbon materials, unstable edge sites can easily convert to structurally stable loop structures. Hence, in the present work, carbon edges are physically passivated via high-temperature treatment in the presence of boron atoms to accelerate loop formation. The highly accelerated loop formation, along with stacking multi-layers at the carbon edges, is systematically investigated via high resolution transmission electron micro microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy and thermal gravimetric analysis (TGA). The boron-added carbon nanofibers (CNFs) at high temperature exhibit a greatly enhanced electrical conductivity due to the high mobility of boron atoms within the carbon structure. In particular, engineering of the loop structures on the carbon edges can alter the overall electrocatalytic activities of the carbon-based materials, as demonstrated in the reductive conversion of 4-nitrophenol (4-NP) and in the hydrogen evolution reaction (HER). This work not only suggests suitable methods for carbon edge passivation, but also opens up a route towards the advanced design of high-stability carbon materials in various fields.