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

Abstract

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/CeH2.73 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 CeH2.73 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).