期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：20
页码：8113-8116
DOI：10.1073/pnas.0903511106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We studied ammonia borane (AB), NH3BH3, in the presence of excess hydrogen (H2) pressure and discovered a solid phase, AB(H2)x, where x {approx}1.3-2. The new AB-H2 compound can store an estimated 8-12 wt % molecular H2 in addition to the chemically bonded H2 in AB. This phase formed slowly at 6.2 GPa, but the reaction rate could be enhanced by crushing the AB sample to increase its contact area with H2. The compound has 2 Raman H2 vibron peaks from the absorbed H2 in this phase: one ({nu}1) at frequency 70 cm-1 below the free H2 vibron, and the other ({nu}2) at higher frequency overlapping with the free H2 vibron at 6 GPa. The peaks shift linearly over the pressure interval of 6-16 GPa with average pressure coefficients of d{nu}1/dP = 4 cm-1/GPa and d{nu}2/dP = 6 cm-1/GPa. The formation of the compound is accompanied by changes in the N-H and B-H stretching Raman peaks resulting from the AB interactions with H2 which indicate the structural complexity and low symmetry of this phase. Storage of significant amounts of additional molecular H2 in AB increases the already high hydrogen content of AB, and may provide guidance for developing improved hydrogen storage materials.
