Kinetic limitations in the Mg–Si–H system

Magnesium silicide (Mg 2 Si) has attracted interest as a hydrogen storage material due to favorable thermodynamics (Δ H desorption  = 36 kJ/mol H 2 ) for room temperature operation. To date, direct hydriding of Mg 2 Si under hydrogen gas to form MgH 2 and Si has only been attempted at low pressure and has been hindered by poor kinetics of absorption. In this paper we study the dehydrogenation reaction with in-situ neutron powder diffraction and present results of our attempts to hydrogenate Mg 2 Si under both hydrogen and deuterium gas up to temperatures of 350 °C and pressures of 1850 bar. Even under these extreme absorption conditions Mg 2 Si does not absorb any measureable quantity of hydrogen or deuterium.