American Chemical Society
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Thermal Conversion of Unsolvated Mg(B3H8)2 to BH4 in the Presence of MgH2

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journal contribution
posted on 2021-04-02, 08:29 authored by Angelina Gigante, Noemi Leick, Andrew S. Lipton, Ba Tran, Nicholas A. Strange, Mark Bowden, Madison B. Martinez, Romain Moury, Thomas Gennett, Hans Hagemann, Tom S. Autrey
In the search for energy storage materials, metal octahydrotriborates, M­(B3H8)n, n = 1 and 2, are promising candidates for applications such as stationary hydrogen storage and all-solid-state batteries. Therefore, we studied the thermal conversion of unsolvated Mg­(B3H8)2 to BH4 as-synthesized and in the presence of MgH2. The conversion of our unsolvated Mg­(B3H8)2 starts at ∼100 °C and yields ∼22 wt % of BH4 along with the formation of (closo-hydro)­borates and volatile boranes. This loss of boron (B) is a sign of poor cyclability of the system. However, the addition of activated MgH2 to unsolvated Mg­(B3H8)2 drastically increases the thermal conversion to 85–88 wt % of BH4 while simultaneously decreasing the amounts of B-losses. Our results strongly indicate that the presence of activated MgH2 substantially decreases the formation of (closo-hydro)­borates and provides the necessary H2 for the B3H8-to-BH4 conversion. This is the first report of a metal octahydrotriborate system to selectively convert to BH4 under moderate conditions of temperature (200 °C) in less than 1 h, making the MgB3H8-MgH2 system very promising for energy storage applications.