The current solutions to efficient hydrogen storage in the solid state greatly rely on dry preparative pathways involving mechanochemical reactions, as exemplified by the reaction equation of formation of novel complex H-rich metal borohydrides: x M1BH4 + M2Clx ? x M1Cl + M2(BH4)x  where M1 is usually Li,                              (1) followed by:y M3BH4 + M2(BH4)x ? M3yM2(BH4)x+y where M3 is an electropositive metal.          (2) The serious drawbacks of this approach consist of (i) lack of scalability and safety problems associated with high-energy milling of large quantities of air- and moisture-sensitive hydride materials, (ii) incomplete yield, (iii) presence of LiCl (or other) dead mass, which decreases the effective H content of the product (by at least 50%) and is inseparable from the borohydride of interest using physical means (because nanocrystals of both products are in-grown into each other), and (iv) inapplicability of this method for synthesis of metastable (i.e. thermodynamically metastable) borohydrides. We have recently developed a method which overcomes most of these problems; our approach relies on the classical wet synthesis inorganic solvents, but also utilizes methathetic reactions, for example: x M1Cl + M2(BH4)x + y ABH4 ? x M1Cl + Ay[M2(BH4)x+y]                                         (3)where L1 is usually Li, and A is a weakly coordinated cation (and ABH4 is soluble in organic solvents) followed by separation of M1Cl (insoluble) and Ay[M2(BH4)x+y] (soluble),                 (4) then by methathesis (again in organic solvents):Ay[M2(BH4)x+y] + y M3L ? y AL + M3y M2(BH4)x+y                                                  (5)where L is a weakly coordinating anion (and M3L is soluble in organic solvents)    and finally by separation of AL (soluble) and Ay[M2(BH4)x+y] (insoluble).                (6) In this contribution we will present the details of the method and its extension from the initial case of M2 = Y(III) to other M2 transition metal cations.

New scalable wet fluorine chemistry method for preparation of dead-mass free hydrogen storage materials

248th National Meeting (2014)

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