In Situ Synchrotron X-ray Diffraction Studies of Hydrogen-Desorption Properties of 2LiBH(4)–Mg(2)FeH(6) Composite

Adding a secondary complex metal hydride can either kinetically or thermodynamically facilitate dehydrogenation reactions. Adding Mg(2)FeH(6) to LiBH(4) is energetically favoured, since FeB and MgB(2) are formed as stable intermediate compounds during dehydrogenation reactions. Such “hydride destabilisation” enhances H(2)-release thermodynamics from H(2)-storage materials. Samples of the LiBH(4) and Mg(2)FeH(6) with a 2:1 molar ratio were mixed and decomposed under three different conditions (dynamic decomposition under vacuum, dynamic decomposition under a hydrogen atmosphere, and isothermal decomposition). In situ synchrotron X-ray diffraction results revealed the influence of decomposition conditions on the selected reaction path. Dynamic decomposition of Mg(2)FeH(6)–LiBH(4) under vacuum, or isothermal decomposition at low temperatures, was found to induce pure decomposition of LiBH(4), whilst mixed decomposition of LiBH(4) + Mg and formation of MgB(2) were achieved via high-temperature isothermal dehydrogenation.