Controlling nanocrystallization and hydrogen storage property of Mg-based amorphous alloy via a gas-solid reaction

A valid strategy via a gas-solid reaction for preparing Mg-based nanocomposite with controllable crystallite size and suitable for massive production is proposed. The nanocomposites consisting of well-dispersed catalytic nano-Mg₂NiH₄/CeH_2.73 embedded in the nano-MgH₂ matrix with crystallite sizes of all phases below 10 nm are fabricated via controlling activation temperature and hydrogen gas (H₂) pressure upon the amorphous Mg₈₀Ce₁₀Ni₁₀ alloy. Increasing H₂ pressure and reducing temperature are beneficial for obtaining fine hydrides, leading to lowered hydrogen desorption temperature. MgH₂ and CeH_2.73 gradually grow up with the increase of de-/re-hydrogenation cycles, while Mg₂NiH₄ remains stable during cycling. After 15 de-/re-hydrogenation cycles, the finest nanocomposite shows remarkably reduced activation energy of dehydrogenation of 87 ± 7 kJ/mol (∼160 kJ/mol for commercial MgH₂).