The hydrogen adsorption capacity of dual-Ti-doped (7, 7) single-walled carbon nanotube (Ti-SWCNTs) has been studied by the first principles calculations. Ti atoms show different characters at different locations due to local doping environment and patterns. The dual-Ti-doped SWCNTs can stably adsorb up to six H-2 molecules through Kubas interaction at the Ti-2 active center. The intrinsic curvature and the different doping pattern of Ti-SWCNTs induce charge discrepancy between these two Ti atoms, and result in different hydrogen adsorption capacity. Particularly, eight H-2 molecules can be adsorbed on both sides of the dual-Ti decorated SWCNT with ideal adsorption energy of 0.198 eV/H-2, and the physisorption H-2 on the inside Ti atom has desirable adsorption energy of 0.107 eV/H-2, ideal for efficient reversible storage of hydrogen. The synergistic effect of Ti atoms with different doping patterns enhances the hydrogen adsorption capacity 4.5H(2)s/Ti of the Ti-doped SWCNT (VIII), and this awaits experimental trial. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.