Controllable decomposition of Ca(BH4)2 for reversible hydrogen storage

Abstract

Ca(BH₄)₂ could reversibly store 9.6 wt% hydrogen based on the overall reaction of Ca(BH₄)₂ → 1/3CaB₆ + 2/3CaH₂ + 10/3H₂. Formation of CaB₆ instead of elemental boron and/or high boranes (e.g. CaB₁₂H₁₂) in the dehydrogenation process is crucial for rehydrogenation. Here, we reported two experimental protocols regarding how to form CaB₆ from the decomposition of Ca(BH₄)₂: (1) decomposition below the melting point, e.g. 350 °C via CaB₂H₆ to CaB₆ and (2) decomposition above the melting point, e.g. 400 °C via elemental boron to CaB₆.