Article,
Magnesium borohydride Mg(BH4)2 for energy applications: A review
Affiliations
- [1] Hefei General Machinery Research Institute (China) [NORA names: China; Asia, East];
- [2] Sichuan University [NORA names: China; Asia, East];
- [3] Aarhus University [NORA names: AU Aarhus University; University; Denmark; Europe, EU; Nordic; OECD];
- [4] Université Catholique de Louvain [NORA names: Belgium; Europe, EU; OECD];
- [5] École Normale Supérieure - PSL [NORA names: France; Europe, EU; OECD];
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Abstract
Mg(BH4)2 with several polymorphs, known as a high capacity (14.9 wt.%) hydrogen storage material, has become more intriguing due to the recently found new functions of gas physisorption and ionic conductivity. Here we review the state-of-the-art on the energy related functions of Mg(BH4)2. Mg(BH4)2 tends to form the stable intermediate [B12H12]2− when the dehydrogenation temperature is above 400 °C, the strong B-B bonding of which makes the rehydrogenation condition very harsh. In contrast, lower borane intermediate [B3H8]2− facilitates the rehydrogenation even at a mild condition of 100 °C, suggesting the possibility of reversible hydrogen storage in Mg(BH4)2. The porous polymorph γ-Mg(BH4)2 shows attractive gas adsorption properties in view of its unique hydridic surface and pore shape, and potentially can be applied in hydrogen adsorption and Kr/Xe selectivity. A new diffraction-based adsorption methodology was developed to characterize adsorption thermodynamics and kinetics of γ-Mg(BH4)2, providing a novel idea for the characterization of crystalline porous materials. Moreover, the potential of Mg(BH4)2 as an electrolyte is discussed in the last part. Mg(BH4)2·THF/DME acts as a liquid electrolyte in Mg-batteries, while anion substituted or neutral molecule derivatives of Mg(BH4)2 can act as solid-state electrolyte.