Hydrolysis of Ammonia Borane as a Hydrogen Source: Fundamental Issues and Potential Solutions Towards Implementation

Abstract

In today's era of energy crisis and global warming, hydrogen has been projected as a sustainable alternative to depleting CO(2)-emitting fossil fuels. However, its deployment as an energy source is impeded by many issues, one of the most important being storage. Chemical hydrogen storage materials, in particular B-N compounds such as ammonia borane, with a potential storage capacity of 19.6 wt % H(2) and 0.145 kg(H2)L(-1), have been intensively studied from the standpoint of addressing the storage issues. Ammonia borane undergoes dehydrogenation through hydrolysis at room temperature in the presence of a catalyst, but its practical implementation is hindered by several problems affecting all of the chemical compounds in the reaction scheme, including ammonia borane, water, borate byproducts, and hydrogen. In this Minireview, we exhaustively survey the state of the art, discuss the fundamental problems, and, where applicable, propose solutions with the prospect of technological applications.

Transition metal-catalyzed dehydrogenation of hydrazine borane N2H4BH3 via the hydrolysis of BH3 and the decomposition of N2H4

“…Despite higher effective GHSCs [9], its potential use has been strongly moderated by the release of undesired ammonia NH 3 concomitantly with the evolution of H 2 . In fact, the underlying problem with the NH 3 group in NH 3 BH 3 is that the recovery of its 3 protic atoms (H dþ ) is thermodynamically impossible in ambient conditions [10]. However, the potential of ammonia borane in chemical hydrogen storage can be valorized in thermolysis, where both H dþ and hydridic hydrogen (H dÀ ) can be recovered as H 2 [11e13].…”

Gaining insight into the catalytic dehydrogenation of hydrazine borane in water

“…Consistently with the pH measurements, the concentration of NH 3 was stable during stage 2. This may be explained by three different reasons: (i) reaction (6) would predominate during stage 2 while both reactions (4) and (6) would occur during stage 1; (ii) the violent H 2 bubbling in stage 1 would force the desorption (from the nanocatalyst surface) and evolution of some NH 3 e this would suppose that the formation of N 2 and H 2 passes through the formation of the adsorbed intermediate NH 3 ; (iii) like in hydrolysis of ammonia borane [14], the violent H 2 bubbling in stage 1 would lead to evaporation of some dissolved NH 3 .…”

Alkaline Ammonia Electrolysis on Electrodeposited Platinum for Controllable Hydrogen Production

“…The electrodeposited Pt electrodes were characterized using SEM (Hitachi, S-4700) and XRD (Rigacku, Miniflex II). To investigate the effect of pH on ammonia oxidation, CVs were conducted in various electrolytes containing 50 mm NH 3 at pH values of 7.9, 10.15, 11.34, and 12.86. The pH was controlled by ab uffer solution containing appropriate amounts of KH 2 PO 4 , K 2 HPO 4 ,a nd K 3 PO 4 (Sigma-Aldrich).…”