The aim of this study was to synthesize the carbon-based nanomaterials and determine their hydrogen storage capacities. Carbon nanotubes (CNTs) were first synthesized by chemical vapor deposition (CVD) of acetylene (C2H2) on a magnesium oxide (MgO) powder impregnated with an iron nitrate (Fe(NO3)(3)center dot 9H(2)O) solution. The synthesis parameters were selected as the synthesis temperatures of 500 and 800 degrees C, the iron content in the precursor of 5% and the synthesis time of 30 minutes. The synthesized material was purified by using HCl at 75 degrees C for 15 hours. After synthesis of CNTs, the polyaniline-doped H3BO3 and BF3 and composites were prepared by coagulation method. The synthesized CNTs and composites were characterized by transmission electron microscopy, FT-IR spectroscopy, Raman spectroscopy and thermogravimetric analyzer. The BET specific surface areas were obtained from the nitrogen adsorption isotherms at -196 degrees C. The hydrogen storage capacities of these carbonaceous materials were measured using volumetric method. It was found that the hydrogen adsorption capacities were changed in the range between 0.44 and 3.67wt% at the liquid nitrogen temperature and gas pressure up to 100 bar.