Cesium hydrazinidoborane, the last of the alkali hydrazinidoboranes, studied as potential hydrogen storage material

Alkali hydrazinidoboranes MN 2 H 3 BH 3 (M = Li, Na, K, Rb) have been developed for hydrogen storage. To complete the family of MN 2 H 3 BH 3, we focused on cesium hydrazinidoborane CsN 2 H 3 BH 3 (CsHB). It has been synthesized by reaction of cesium with hydrazine borane (N 2 H 4 BH 3 ) at −20 °C under inert atmosphere, and it has been characterized. A crystalline solid (monoclinic, s.g. P 2 1 (No. 4)) has been obtained. Its potential for hydrogen storage has been studied by combining different techniques. It was found that, under heating at constant heating rate (5 °C min −1 ) or at constant temperature (e.g. 120 °C), CsHB decomposes rather than it dehydrogenates. It releases several unwanted gaseous products (e.g. NH 3, B 2 H 6 ) together with H 2, and transforms into a residue that poses safety issues because of shock-sensitivity and reactivity towards O 2 /H 2 O. Though the destabilization brought by Cs + onto the anion [N 2 H 3 BH 3 ] − has been confirmed, the effect is not efficient enough to avoid the aforementioned drawbacks. All of our results are presented herein and discussed within the context of solid-state hydrogen storage.