A theoretical study on cage-like clusters (C12Ti6 and C12Ti62+) for dihydrogen storage

Abstract

Abstract This work reports the dihydrogen adsorption and storage capacity of cage-like clusters (C12 Ti6 and C12 Ti62+) using density functional theory calculations. The neutral system C12 Ti6 can adsorb 15 hydrogen molecules, however, some hydrogen molecules will dissociate and bond atomically on titanium atoms. The strong binding energy will cause high operating temperature to desorb hydrogen during the application process. Fortunately, the cationic system C12 Ti62+ can adsorb up to 16H2 all in molecular form. Moreover, the predicted maximal hydrogen storage density is 6.96\xa0wt% and the average adsorption energies of C12 Ti62+ (nH2) (n\xa0=\xa01–16) are in the desirable range of reversible hydrogen storage at the 6-311G(d,p)-B3LYP and M06-2X levels. The interaction of C12 Ti62+ with hydrogen molecules is considered by means of the bond critical points (bcp) in the quantum theory of atoms in molecules (QTAIM). With respect to Gibbs free energy corrected H2 adsorption energy, C12 Ti62+ adsorbs 16H2 molecules should be at low temperature (190\xa0K). These predictions show that cationic C12 Ti62+ is more suitable as a material for adsorbing dihydrogen.