"Synthesis of nitrogen-doped carbon nanotubes from polymeric precursors (polystyrene and polypyrrole) by poly-condensation followed by carbonization under an inert atmosphere is reported. Three different carbonization temperatures (500 degrees C, 700 degrees C and 900 degrees C) were employed to synthesize three different carbon nanostructures with different morphologies. These were designated as NCNR-500 (nitrogen-doped carbon nanorods), NCBCT700 (nitrogen-doped fused bead carbon nanotubes), and NCNT-900 (nitrogen-doped carbon nanotubes) according to morphology and carbonization temperature. Microstructure, morphology, porosity, and nitrogen content were characterized by several different techniques. The effects of carbonization temperature and the role of functional groups were also investigated. Total and excess hydrogen storage capacities of 2.0 wt% and 1.8 wt%, respectively, were measured at 298 K and 100 bar for the NCNT-900 material. This is higher than the capacities of the NCNR-500 and NCBCT-700 materials. NCNT-900 exhibited a porous structure with high specific surface area and total pore volume of 870 m/g and 0.62 cm(3)/g, respectively. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.