Alkali, alkaline earth and transition metal doped B6H6 complexes for hydrogen storage

Alkali, alkaline earth and transition metal doped B6H6 complexes are considered for the hydrogen storage. Density functional theory (DFT) and second order Møller-Plesset methods with 6-311++G** basis set have been used for the study. B6H6Li, B6H6Be, B6H6Sc, B6H6Li2, B6H6Be2, B6H6Sc2 complexes can interact with maximum three, two, four, six, four and eight H2 molecules respectively with respective H2 uptake capacity of 7.2, 4.8, 6.5, 12.5, 8.3 and 9.1 wt%. This uptake capacity is well above the target set by the U.S. Department of Energy by 2020 except for the B6H6Be complex. Thermo chemistry calculations are carried out to estimate the Gibbs free energy corrected H2 adsorption energy which reveals whether adsorption of hydrogen on these complexes is favourable or not at different temperature. It is observed that H2 adsorption on all the six complexes are unfavourable at ambient conditions where as it is favourable below 150, 135, 75, and 50 K on B6H6Sc, B6H6Be, B6H6Li and B6H6Li2 complexes respectively. Various interaction energies in H2 adsorbed complexes are obtained using Many-body analysis approach. The H2 desorption temperature for the B6H6Li, B6H6Be, B6H6Sc, B6H6Li2, B6H6Be2 and B6H6Sc2 complexes is found to be 25, 165, 265, 10, 265 and 373 K respectively.