Nanostructural Perspective for Destabilization of Mg Hydride Using the Immiscible Transition Metal Mn

Phase segregation in hydride-forming alloys may persist under the action of multiple hydrogenation/dehydrogenation cycles. We use this effect to destabilize metal hydrides in the immiscible Mg-Mn system. Here, in the MgMn_1- thin films, the Mg and Mn domains are chemically segregated at the nanoscale. In Mn-rich compositions, the desorption pressure of hydrogen from MgH₂ is elevated at a given temperature, indicating a thermodynamic destabilization. The increase in the desorption pressure of hydrogen reaches ∼2.5 orders in magnitude for x = 0.30 at moderate temperatures. Such large thermodynamic destabilization allows the MgH₂ to reversibly absorb and desorb hydrogen even at room temperature. Our strategy to use immiscible elements for destabilization of MgH₂ is effective and opens up the possibility for the development of advanced and low-cost hydrogen storage and supply systems.