In this project, first of all the iron Nano particles loaded on calcium carbonate surface via sol-gel method to produce Fe/CaCO 3 catalyst. Then, the condition of chemical vapor deposition (CVD) such as argon flew, annealing time, rate of temperature were optimized for synthesis of carbon nanotubes doped with some elements like phosphorous, sulfur and nitrogen from various precursors (solid, liquid and gas). In next section, the nitrogen doped carbon nanotubes were synthesized with high percentage of nitrogen (6.63%) by the help of acetonitrile precursor. The structures, sizes and specifications of prepared carbon nanotubes were determined and confirmed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy, Energy dispersive X-ray spectroscopy (EDX), X-Ray diffraction (XRD) and cyclic voltammetry (CV). Based on FESEM pictures, the average size of nanotubes reduced from 40 to 29 nm after optimization. Elemental distribution within structures approved by EDX analysis. Spiral morphology of synthesized nanotubes also confirmed by TEM analysis. Structural ordering about the doped CNTs was observed from Raman spectra. Electrochemical behavior of these products investigated by cyclic voltammetry, which suggest catalytically activity of them. In another section of this project, the phosphorous and sulfur dual doped carbon nanotubes were synthesized from triphenylphosphine and sulfur precursors. The percentage of phosphorous and sulfur was observed about 1.57% and 2.26% respectively from EDX. In last section, phosphorous doped carbon nanotubes were synthesized via retreatment of previously prepared CNTs with triphenylphosphine and analyzed. The diameter of PCNTs confirmed about 40 nm by FESEM. The TEM pictures revealed that the modified PCNTs were with the agglomerated morphology. So the presented methods could be employed as an efficient, fast and low cost technique for preparation of doped carbon nanostructures.
