Surface-Controlled Conversion of Ammonia Borane from Boron Nitride

Tessui Nakagawa,Benjamin L Davis,Hiroki Uesato,Anthony K Burrell,Hiroki Miyaoka,Yoshitsugu Kojima,Takayuki Ichikawa

doi:10.3390/en13215569

Tessui Nakagawa, Benjamin L Davis + Show 5 more

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https://doi.org/10.3390/en13215569

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Abstract

“One-pot regeneration”, which is simple regneneration method of ammonia borane (AB) using hydrazine and liquid ammonia, enables conversion of AB from hexagonal boron nitride (h-BN) after milling hydrogenation. Solution 11B-NMR revealed the presence of AB after NH3/N2H4 treatment of milled h-BN (BNHx) although the yield of AB was less than 5%. The conversion mechanism was clarified as B-H bonds on the h-BN surface created by ball-milling under hydrogen pressure have an ability to form AB, which was confirmed by Thermogravimetry-Residual Gas Analysis (TG-RGA) and Infrared (IR) analysis. The reaction routes are also the same as regeneration route of polyborazylene because intermediates of AB such as (B(NH2)3 and hydrazine borane were found by solution 11B-NMR after soaking BNHx in liquid NH3 and hydrazine, respectively. Because of the fact that all reactions proceed on the h-BN surface and no reaction proceeds when neat h-BN is treated, breaking of B3N3 ring structure and then creation of B-H bond is the key issue to increase conversion yield of AB.

Highlights

In the future, a major hurdle of realizing carbon constraining world is storage and transportation of energy
Hydrazine borane (HzB) can be produced as an intermediate compound or by the reaction between ammonia borane (AB) and N2 H4, in liquid NH3 all of hydrazine borane (HzB) can be converted to AB by metathesis (Figure 2b)
The synthesis of AB from hexagonal boron nitride (h-BN) was successful using ball milling under hydrogen pressure and soaked in N2 H4 -liquid NH3 solution

Summary

Introduction

A major hurdle of realizing carbon constraining world is storage and transportation of energy. While there are many potential green sources of electrical energy generation (e.g., solar and wind), both the intermittency and remoteness of these sources will severely limit their practical application at large scale [1]. Hydrogen generated from electrolysis suffers from several drawbacks: it is a gas and requires either large volumes or high pressures to store [2]. Similar issues arise in the application of hydrogen as a fuel in automotive applications. The commercial hydrogen fuel cell vehicle can store 70 MPa of hydrogen with about 5.5 mass% including tank, improvement of hydrogen storage technology with higher hydrogen density (U.S DOE ultimate target: 6.5 mass% of system) is required [2]. The promising way to store hydrogen with high density is hydrogen storage material; many different hydrogen

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