One of the major issues associated with the use of borohydride complexes for hydrogen storage is the thermodynamic stability of these materials, with the Group I and II complexes also requiring the most demanding temperatures to facilitate dehydrogenation. In recent years, the idea of modulating thermodynamic properties by combining metals with different stabilities (as monocation borohydrides) has come to light. By incorporating a cation with ionic bonding characteristics, it has been proposed that the volatile Sc borohydrides can be stabilized to an extent that diborane release is prevented. We show, using in situ IR and TG analysis, that these complexes do indeed release significant quantities of diborane, which is an irrevocable barrier to reversibility. Our findings suggest that the Group I/Sc bimetallic borohydrides are not suitable for hydrogen storage.
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