High hydrogen capacity and reversibility of k-decorated silicon materials

We have investigated the H2 adsorption structures and binding energies of the metal (M)-doped (M = Li, Na, K, Mg, and Al) silicon complexes, M-Si19H11 and M-Si24H12, using density functional calculations. Alkali metals are preferred as doping elements because the Mg-Si and Al-H2 interactions are weak. The maximum numbers of H2 molecules that can be adsorbed are four and five for M=Li and K, respectively. We propose that the K-decorated silicon material might be an effective hydrogen storage material with high hydrogen capacity and high reversibility.