Theoretical study of hydrogen storage in Li-decorated Al12N12 clusters

Abstract

The hydrogen storage capacity of Li-decorated Al12N12 clusters is investigated using density functional theory computations. The present results indicate that Li atoms are strongly attached on tops of N atoms of the Al12N12 nanocage, forming Al12N12Lim (m = 1, 2, 4, 8, 12) complexes. The binding energies of the Li atoms on the Al12N12 are in the range of 1.60–1.95 eV, which are larger than that among Li atoms. The clustering of Li atoms can be effectively prevented on the surface of the host. The charge transfer from Li atoms to the Al12N12 makes Li atoms positively charged. Each Li atom in the Li-decorated Al12N12 complexes can adsorb a maximum of 3 H2 molecules with the average adsorption energy of 0.09–0.12 eV/H2. The polarization interaction is responsible for the adsorption of H2 molecules to Li-decorated Al12N12 complexes. The fully coated Al12N12Li12 complex can hold up to 36 H2 molecules, and the corresponding gravimetric density of hydrogen is 11.2 wt%, far exceeding the ultimate target of 6.5 wt% of U. S. DOE.