Facile solid-phase synthesis of the diammoniate of diborane and its thermal decomposition behavior

Abstract

The recent mechanistic finding of the hydrogen release pathways from ammonia borane (AB) has sparked new interest in the chemistry and properties of the diammoniate of diborane (DADB), an ionic isomer of AB. We herein report a facile one-step solid-phase synthesis route of DADB using inexpensive starting materials. Our study found that mechanically milling a 1 : 1 NaBH(4)/NH(4)F powder mixture causes the formation of crystalline DADB via a NH(4)BH(4) intermediate. The produced DADB can be readily separated from the sodium fluoride (NaF) by-product by a purification procedure using liquid ammonia at -78 °C. The thermal decomposition behavior of DADB was studied using synchronous thermal analyses, particularly in comparison with AB. It was found that the decomposition steps and products of DADB are similar to those of AB. But meanwhile, DADB exhibits a series of advantages over AB that merit its potential hydrogen storage application, such as lower dehydrogenation temperature, free of foaming and lack of an induction period in the thermal decomposition process. Our study further found that the volatile non-hydrogen products from DADB can be effectively suppressed by milling with MgH(2).

Time dependent decomposition of ammonia borane for the controlled production of 2D hexagonal boron nitride

“…3 ). The FTIR features can be readily assigned to different modes 43 . Fundamentally different bonding between B-N in AB and DADB means that these can be distinguished from the B-N stretch mode in the 600 cm −1 –900 cm −1 region 43 .…”

“…The FTIR features can be readily assigned to different modes 43 . Fundamentally different bonding between B-N in AB and DADB means that these can be distinguished from the B-N stretch mode in the 600 cm −1 –900 cm −1 region 43 . AB has three characteristic peaks at 726 cm −1 , 782 cm −1 and 798 cm −1 , while DADB has two wider separated main peaks at ~667 cm −1 , ~853 cm −1 and two smaller peaks 43 .…”

Synthesis of Ammonia Borane Nanoparticles and the Diammoniate of Diborane by Direct Combination of Diborane and Ammonia

“…Meanwhile, DADB the ionic dimer of AB that has also attracted much attention as hydrogen‐storage candidate, remains difficult to synthesize due to the rigorous procedure of the original synthesis and DADB's instability in organic solvents at ambient temperature . Currently, there is no commercial source of DADB and the existing preparative methods, the reaction of liquid ammonia with borane, decomposition of NH 4 BH 4 , or ball milling NaBH 4 and NH 4 F are not suitable for commercialization. The absence of a facile synthesis has become a barrier for the comprehensive study of this advanced material, and a practical synthesis method is still urgently needed.…”

11 B MAS NMR Study of the Thermolytic Dehydrocoupling of Two Ammonia Boranes upon the Release of One Equivalent of H2 at Isothermal Conditions

“…The 11 B spectrum of 2 0 presents additional Gaussian/Lorentzian signals of low intensity (Figure ). The signals located at ‐38 and ‐17 ppm are due to DADB ,,,. The signal located at ‐12 ppm is ascribed to the B H 2 N 2 environment, which is typical of PAB ,,.…”