Reversibility of LiBH4 Facilitated by the LiBH4-Ca(BH4)2 Eutectic

The hydrogen storage properties of eutectic melting 0.68LiBH4–0.32Ca(BH4)2 (LiCa) as bulk and nanoconfined into a high surface area, SBET = 2421 ± 189 m2/g, carbon aerogel scaffold, with an average pore size of 13 nm and pore volume of Vtot = 2.46 ± 0.46 mL/g, is investigated. Hydrogen desorption and absorption data were collected in the temperature range of RT to 500 °C (ΔT/Δt = 5 °C/min) with the temperature then kept constant at 500 °C for 10 h at hydrogen pressures in the range of 1–8 and 134–144 bar, respectively. The difference in the maximum H2 release rate temperature, Tmax, between bulk and nanoconfined LiCa during the second cycle is ΔTmax ≈ 40 °C, which over five cycles becomes smaller, ΔTmax ≈ 10 °C. The high temperature, Tmax ≈ 455 °C, explains the need for high temperatures for rehydrogenation in order to obtain sufficiently fast reaction kinetics. This work also reveals that nanoconfinement has little effect on the later cycles and that nanoconfinement of pure LiBH4 has a strong effect in o...