First-principles computational study of hydrogen storage in silicon clathrates

Figures & data

Figure 1. The relative gravimetric performance of physisorption, spillover, and chemisorption (complex hydride) materials towards achieving the minimum material-based targets for on-board reversible fuel storage (from Miller et al. [2]).

Figure 2. (a) Extended crystal structure of the intermetallic clathrates (Type I). Red = volume space for guest atoms such as Ba, Na, and Li. Blue = substitutional framework atoms such as C, Al, and Cu. The unit cell is indicated by grey box. (b) Occupiable volume for H₂ exists in the cages of both the 20-atom pentagonal dodecahedron clusters (2a Wyckoff sites) and 24-atom tetrakaidecahedron clusters (6d Wyckoff sites).

Figure 3. Predicted internal binding energy and capacity for intermetallic clathrates. The range over which binding interactions of H₂ is favourable for room temperature storage is noted (a) hydrogenation of Si₄₆, C₆Si₄₀, Ba₈Al₈Si₃₈, and Ba₈Cu₈Si₃₈ and (b) hydrogenation of Si₄₆, C₆Si₄₀, Na₈Al₈Si₃₈, and Li₈Al₈Si₃₈.

Figure 4. Predicted gravimetric capacity (materials basis) and lattice constant for intermetallic (hybrid) clathrates: (a) hydrogenation of Si₄₆, C₆Si₄₀, Ba₈Al₈Si₃₈ and Ba₈Cu₈Si₃₈ and (b) hydrogenation of Si₄₆, C₆Si₄₀, Na₈Al₈,Si₃₈, and Li₈Al₈Si₃₈. Vertical lines mark the system-level targets prescribed by DOE.

Figure 5. Predicted volumetric capacity and lattice constant for intermetallic clathrates: (a) hydrogenation of Si₄₆, C₆Si₄₀, Ba₈Al₈Si₃₈, and Ba₈Cu₈Si₃₈ and (b) hydrogenation of Si₄₆, C₆Si₄₀, Na₈Al₈Si₃₈, and Li₈Al₈Si₃₈. Vertical lines mark the system-level targets prescribed by DOE.

Miller MA, Page RA. Standardized testing program for solid-state hydrogen storage technologies. Final report for the Department of Energy hydrogen and fuel cells program, Contract No. DEFC3602AL67619. San Antonio, TX: Southwest Research Institute; 2012 July 30.

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