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

•A strategy via gas-solid reaction for preparing Mg-based nanocomposite is proposed.•Mg2NiH4/CeH2.73 well disperse in MgH2 matrix with crystallite sizes all below 10 nm.•Activation energy of dehydrogenation is reduced to 87 ± 7 kJ/mol.

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).

Graphical abstractA valid strategy via a gas-solid reaction for preparing nanomaterials with controllable crystallite size and suitable for massive production is proposed. Higher H2 pressure and lower temperature are beneficial for obtaining finer hydrides with remarkably reduced dehydrogenation activation energy.Figure optionsDownload full-size imageDownload as PowerPoint slide