Synthesis, morphology, magnetic and electrochemical studies of nitrogen-doped multiwall carbon nanotubes fabricated using banded iron-formation as catalyst

Natural catalysts are important for the low-cost and large-scale production of carbon nanostructures. In this study, we used a natural material obtained from thin bands of sedimentary rocks known as Banded Iron Formation (BIF). BIF powders (pristine and ball-milled) were used as catalysts for the large-scale production of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) via an aerosol-assisted catalytic chemical vapor deposition (AACCVD) experiment. The morphology and composition profiles of the BIF powders and N-MWCNT samples were analyzed by scanning and transmission electron microscopies, X-ray diffraction, X-ray photoelectron (XPS) and Raman spectroscopies, and thermogravimetric analysis. XRD characterizations revealed that the BIF powders were mainly composed of quartz and hematite. This result was also confirmed by Raman spectroscopy. The production efficiency of 340% wt./wt. of the N-MWCNTs was obtained by 1 h ball-milled BIF powders. The specific surface area of the N-MWCNTs reached 37.87 m(2)/g. The type of nitrogen doping, oxygen functional groups, silicon, and carbon species (sp(2) and sp(3)) hosted at the surface of the N-MWCNTs were quantified by XPS. The electrochemical response of electrodes composed of the N-MWCNTs were studied via cyclic voltammetry, electrochemical impedance, and coulombic efficiency determination to assess the possible applications of our synthesized materials as energy storage or sensor systems. The magnetic properties and effects of acid and thermal treatments on the morphology of the N-MWCNTs are also presented. (C) 2020 Elsevier B.V. All rights reserved.