Abstract
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Magnesium-based hydrides represent a particularly promising
candidate for hydrogen storage because of their high gravimetric
and volumetric hydrogen capacities, high abundance
(≈2.5% of Earth’s surface composition, and virtually in
unlimited amounts in sea water), low cost, nontoxicity, and
high safety. [ 1 ] Their thermodynamic stability, the slow kinetics
of their reversible H 2 storage reaction, and their inherent low
thermal conductivity, however, signifi cantly obstruct their
practical application in fuel cells. [ 2,3 ] To date, one of the most
effective techniques to relieve the kinetic barrier and/or thermodynamics
stability of Mg-based hydrides is nanostructuring, [ 4 ]
which could directly result in a larger surface-to-volume ratio
of the particles, shorter solid-state diffusion distances for
hydrogen, and/or decreased thickness of the H 2 -impermeable
layer of MgO. [ 5,6 ] Extensive experimental and theoretical studies
have recently demonstrated that decreasing the particle size
is also capable of thermodynamically destabilizing Mg-based
hydrides, leading to a further enhancement of hydrogen storage
performance.