Enhancing destabilization of MgH2 with reactive elemental additives
Navaratnarajah Kuganathan, Martin Dornheim, David M. Grant, Sanliang Ling
Abstract
Magnesium hydride (MgH₂) holds significant promise as a hydrogen storage material, though its high thermodynamic stability poses challenges. Alloying MgH₂ to destabilize it has emerged as an effective approach to lower its hydrogen desorption temperature and reaction enthalpy. While some specific alloy types with certain elements and their associated dehydrogenation enthalpies have been investigated, the formation of alloys with varied additive elements, diverse stoichiometries, and potential reactions between MgH₂ and the additives, including alloy formation, remains largely unexplored. Here, we use density functional theory (DFT) to explore MgₓA y (x, y = 1, 2, and 3 and A = Group II, III, IV, transition, noble, and post-transition elements) alloy formation and to calculate the dehydrogenation enthalpy associated with hydrogen release from MgH 2 via different reaction routes. Our findings indicate that Rh and Pd strongly tend to form various alloy types, resulting in strong destabilization of MgH 2 in the presence of these elements with exothermic dehydrogenation enthalpies. Elements identified as forming the most stable MgA, Mg 2 A, MgA 2 , MgA 3 and Mg 3 A 2 alloy types, with favorable dehydrogenation enthalpies, include Ag and Ga; Ge, Ni, and Sn; B, Co, Cu, and Zn; Al; and Ru respectively. Furthermore, the stability and dehydrogenation potential of several Mg-A-H ternary hydrides were also evaluated.