Sodium Hydrazinidoborane: A Chemical Hydrogen‐Storage Material

Abstract

Herein, we present the successful synthesis and full characterization (by (11) B magic-angle-spinning nuclear magnetic resonance spectroscopy, infrared spectroscopy, powder X-ray diffraction) of sodium hydrazinidoborane (NaN2 H3 BH3 , with a hydrogen content of 8.85 wt %), a new material for chemical hydrogen storage. Using lab-prepared pure hydrazine borane (N2 H4 BH3 ) and commercial sodium hydride as precursors, sodium hydrazinidoborane was synthesized by ball-milling at low temperature (-30 °C) under an argon atmosphere. Its thermal stability was assessed by thermogravimetric analysis and differential scanning calorimetry. It was found that under heating sodium hydrazinidoborane starts to liberate hydrogen below 60 °C. Within the range of 60-150 °C, the overall mass loss is as high as 7.6 wt %. Relative to the parent N2 H4 BH3 , sodium hydrazinidoborane shows improved dehydrogenation properties, further confirmed by dehydrogenation experiments under prolonged heating at constant temperatures of 80, 90, 95, 100, and 110 °C. Hence, sodium hydrazinidoborane appears to be more suitable for chemical hydrogen storage than N2 H4 BH3 .

In situ Synchrotron X-ray Thermodiffraction of Boranes

“…The diffraction patterns were successfully indexed in the monoclinic phase with the space group P2 1 /n ( Figure S16). The unit cell parameters extracted at 81 K are reported in Table 1, and are in agreement with the literature [21]. Like for LiHB, the unit cell parameters of NaHB exhibit a positive evolution (Figure 10) and the unit cell volume presents a normal evolution with positive coefficient of thermal expansion ( Figure S17).…”

“…With NaHB, the sodium cation is surrounded by five symmetry-equivalent anions [4,21]. The bigger size of Na + (116 pm vs. 90 pm for Li + ) explains its higher coordination degree and the bigger unit cell volume of NaHB.…”

“…Synthesis of AB, HB, HBB, LiHB, NaHB, and STB were carried out according to procedures reported in details elsewhere [9,10,15,21,24,25]. After synthesis, the samples were stored in an argon-filled glove box (MBraun M200B, O 2 < 0.1 ppm, H 2 O < 0.1 ppm).…”

Hydrazine Borane and Hydrazinidoboranes as Chemical Hydrogen Storage Materials

“…In particular, they suggested that the initial step would be characterized by the formation of dimers like NH2NH(M)BH2-NHNH(M)BH3 and NH2NH(M)BH=NNH(M)BH3 (with M as Li, Na or K) obtained by intermolecular reactions between H δ+ in one molecule and H δ− in another one. This is in agreement with the hypotheses reported by Moury et al [66,68]. Also, Chua et al [74] highlighted a clear correlation between the cation size and dehydrogenation properties of the metal hydrazinidoborane.…”

“…It is generally admitted that the dehydrogenation of boranes is complex [71], and the reference [72] is further evidence of such complexity. Moury et al [68] investigated the sodium derivative. Sodium hydride NaH showed high reactivity towards hydrazine borane.…”