To meet the U.S. Department of Energy requirements for onboard solid-state hydrogen (H2) storage, novel materials such as metal borohydrides have increasingly been investigated, in particular, magnesium borohydride (Mg(BH4)2). While these materials have a high H2 capacity (&gt; 14 wt%), poor hydrogenation-dehydrogenation cyclability and material degradation, e.g.loss of boron, need to be overcome. Prior research has indicated that nano-encapsulation and chemical additives can address these challenges. We pursue these two strategies simultaneously with atomic layer deposition (ALD) on γ-Mg(BH4)2. ALD is a vapor-phase technique successfully used to protect and enhance heterogeneous catalysts. Due to ALD’s self-limiting nature, it can control the amount of additive deposited onto H2-storage materials with great precision. The effect of metal-oxides (e.g.Al2O3, TiO2, CeO2), metal-nitrides (e.g.TiN, BN) and pure metals (e.g.Ru, Pd) as additives to γ-Mg(BH4)2 will be presented and discussed. Compared to the blank γ-Mg(BH4)2, we show that the H2 desorption temperature was lowered to 60 – 120°C, the desorbed gravimetric capacity at temperatures below 250°C was doubled, the desorption kinetics were increased by a factor of ~6, and the formation of diborane was suppressed substantially. The evolution of the γ-Mg(BH4)2 was also explored with respect to the structure, the effects of the total hydrogen capacity, and catalytic effects. Data supporting these results from temperature programmed desorption, pressure composition temperature manometric measurements, inductively coupled plasma mass spectrometry, nitrogen sorption measurements, nuclear magnetic resonance, transmission electron microscopy, and diffraction spectroscopy.

Role of additives on the H2 storage properties of Mg(BH4)2

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.