Hydrogen Sorption from the Mg(NH2)2-KH System and Synthesis of an Amide-Imide Complex of KMg(NH)(NH2)

• Published in: ChemSusChem 2011-11, Vol.4 (11), p.1622-1628
• Main Authors: Wang, Jianhui, Wu, Guotao, Chua, Yong Shen, Guo, Jianping, Xiong, Zhitao, Zhang, Yao, Gao, Mingxia, Pan, Hongge, Chen, Ping
• Format: Article
• Language: English
• Subjects: Amides - chemistry; chemisorption; Chemistry Techniques, Synthetic - methods; hydrogen; Hydrogen - chemistry; Imides - chemistry; magnesium; Magnesium - chemistry; potassium; synthetic methods; Temperature
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201100207

The interaction between KH and Mg(NH2)2 is investigated. Results from temperature‐programmed desorption measurements on samples of [Mg(NH2)2][KH]x (x=0.5, 1.0, and 2.0) indicated that dehydrogenation from [Mg(NH2)2][KH] occurred through a two‐step reaction with an onset temperature as low as 60 °C. Accompanied by hydrogen release, K2Mg(NH2)4 and MgNH successively developed at lower temperatures, whereas KMg(NH)(NH2) developed at higher temperatures. However, when dehydrogenation was conducted under isothermal and near‐equilibrium conditions, a single‐step reaction that led to the formation of KMg(NH)(NH2) was observed. KMg(NH)(NH2) is a new amide–imide complex. The synthesis of KMg(NH)(NH2) can be achieved either by dehydrogenation of the [Mg(NH2)2][KH] mixture or by thermal decomposition of the [K2Mg(NH2)4][Mg(NH2)2] mixture. Uptake and release: The Mg(NH2)2‐KH system can be used for reversible hydrogen storage. For non‐isothermal dehydrogenation of [Mg(NH2)2][KH], K2Mg(NH2)4 and MgNH successively develop at lower temperatures and KMg(NH)(NH2) develops at higher temperatures. However, under isothermal and near‐equilibrium conditions, dehydrogenation is a single‐step process, leading to the formation of KMg(NH)(NH2) (see scheme).