Can ionization induce an enhancement of hydrogen storage in Ti2–C2H4 complexes?

Abstract

We predicted here gravimetric hydrogen storage capacity of Ti₂–C₂H₄ and Ti₂–C₂H₄⁺ complexes using density functional theory (DFT) method. The number of adsorbed H₂ on Ti₂–C₂H₄ is limited to ten. It has been seen that controlling the charge-state of this complex enhances its gravimetric hydrogen uptake and the metal bond strength. The resulting cationized complex then adsorbs two additional H₂ molecules than the neutral complex. In addition, we elucidated the effect of exchange and correlation functionals in DFT on H₂ adsorption energy of these complexes. Molecular dynamics simulations were also carried out to confirm whether the complex adsorbs H₂ molecules at a finite temperature. The H₂ uptake capacity of a complex from simulations is the same as that from the geometry optimization only if the H₂ adsorption was energetically favourable i.e. with the positive Gibbs free corrected H₂ adsorption energy.