High hydrogen storage capacity in calcium-decorated silicene nanostructures

We report our first-principle's calculations on the possibility of Ca-decorated silicene sheet and zigzag silicene nanoribbons (ZSiNRs) as hydrogen storage medium. We predict that Ca atoms prefer to disperse on the silicene or at the edges of ZSiNRs without clustering, due to the strong binding between Ca and Si atoms. By adsorbing Ca atoms on the both sides of silicene, the hydrogen storage capacity can reach to 6.17wt% (gravimetric density) with an average adsorption energy of 0.265eVH(2)(-1), which are quite optimial for reversible hydrogen adsorption and desorption at ambient conditions. The hydrogen storage capacity can be further improved to 8.43wt% with the average adsorption energy in the range of 0.182-0.269eVH(2)(-1) in the Ca-decorated ZSiNRs. The adsorption of H-2 on Ca-decorated Si nanostructures is mainly dominated by polarization and the orbital hybridizations. These findings indicate that the Ca-decorated silicene and ZSiNRs have potential application in hydrogen storage.