First-principles computational study of hydrogen storage in silicon clathrates

Density functional theory (DFT) was utilized to compute the gravimetric capacity, volumetric capacity, and the binding energy of hydrogen molecules in silicon clathrates with guest (A) atoms such as Ba, Na, and Li, and framework substitutional atoms (M) such as C, Al, and Cu. The DFT computations show that these Type I intermetallic clathrates can accommodate a large number of hydrogen molecules, equivalent to 10 wt.%, and such hydrogenated structures, Ax(H2)nMySi46−y, occur with only a modest increase in lattice volume and a binding energy within the desirable range of 0.1–0.6 eV/H2 for hydrogen storage at or near ambient temperature. IMPACT STATEMENT This paper identifies a number of Type I silicon clathrates that can accommodate large amounts of hydrogen molecules (10 wt.%) and may be suitable as hydrogen storage materials.