Sc/Ti decorated novel C_(24)N_(24) cage: Promising hydrogen storage materials

摘要

Inspired by the TM-N-4 coordination environment and the promising hydrogen adsorption property of the Ti-C-4 unit, four novel TM6C24N24 (TM = Sc, Ti) cages with six TM-N-4/TM-C-4 units are designed simultaneously for the first time in this paper. Their stabilities are studied by using DFT calculations and confirmed by MD simulations. Sc6C24N24(N-4) and Ti6C24N24(N-4) can absorb 30 hydrogen molecules and keep the original structures intact. The average hydrogen adsorption energy is 0.13-0.26 eV for Sc6C24N24(N-4)-6nH(2) (n = 1-5), and 0.09-0.23 eV for Ti6C24N24(N-4)-6nH(2) (n = 1-5). The hydrogen storage capacities are 6.30 wt % and 6.20 wt %, respectively. Besides, the 30H(2) can be readily adsorbed on Sc6C24N24(N-4) under 160 K and 100% desorbed at 270 K under 0.1 MPa. The desorption temperature could increase if the pressure becomes higher. Sc6C24N24(C-4)/Ti6C24N24(C-4) complexes are higher in energy than corresponding Sc6C24N24(N-4)/Ti6C24N24(N-4). They are not suitable as room-temperature hydrogen storage materials due to the structural deformation in the hydrogen storage process. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.