De-hybridization effect of transition metal catalysts on AlH4-based hydrogen storage materials

Abstract

Understanding the microscopic impact of catalysis on the de-hydrogenation process of hydrides is crucial for the development of hydrogen storage materials. In this paper, density functional theory calculations are employed to study the adsorption and dissociation of the AlH4 cluster, which is the building block of many complex hydrides, on a series of transition metal surfaces. We find that the hybrid bonding of the AlH4 cluster is weakened when adsorption on metal surfaces and the Al–H bonds are stretched accordingly. This de-hybridization effect enhances from Sc to Ni in correlation with the work function. Based on the results, we predict Ni to be the most effective transition metal in lowering the de-hydrogenation barrier of AlH4-based hydrides. Detail electronic structure analysis show that the de-hybridization effect mainly resulted from the charge transfer between metals surface and AlH4 clusters. Our results provide deep insight into improving the properties of hydrogen storage materials.