AB–MH (Ammonia Borane–Metal Hydride) composites: systematic understanding of dehydrogenation properties

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2014-01, Vol.2 (11), p.3926-3931
• Main Authors: Nakagawa, Yuki, Isobe, Shigehito, Ikarashi, Yudai, Ohnuki, Somei
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/C3TA14670G

Dehydrogenation properties of AB–MH (Ammonia Borane–Metal Hydride, M = K, Na, Li, Ca, Mg, Al) composites were systematically investigated by thermal and mass analyses. The results suggest that the Pauling electronegativity of M, χ p , is a good indicator to predict the phases of composites, the dehydrogenation temperature and the amount of by-product gases (NH 3 and B 2 H 6 ). The phases of composites were classified by χ p as follows. MBH 4 was formed for M = K, Na ( χ p ≤ 0.9), MNH 2 BH 3 was formed for M = Na, Li (0.9 ≤ χ p ≤ 1.0) and no new compounds were formed for M = Ca, Mg, Al (1.0 ≤ χ p ). The 1st dehydrogenation temperatures of the samples (M = Na, Li, Ca, Mg) were 10–20 °C lower than that of AB itself ( χ p ≤ 1.2). The amount of NH 3 was decreased as χ p increased. On the other hand, the amount of B 2 H 6 was decreased as χ p decreased. The emission of B 3 H 6 N 3 could occur by the reaction of NH 3 and B 2 H 6 . Finally, AB–MAlH 4 (M = Na, Li) composites, which were prepared based on the indicator, showed superior potential as hydrogen storage materials because they did not desorb any by-products NH 3 , B 2 H 6 and B 3 H 6 N 3 .