The role of V2O5 on the dehydrogenation and hydrogenation in magnesium hydride: An ab initio study.

Ab initio density functional theory calculations are performed to study the experimentally observed catalytic role of V₂O₅ in the recycling of hydrogen in magnesium hydride. We find that the Mg–H bond length becomes elongated when MgH₂ clusters are positioned on single, two, and three coordinated oxygen sites (O₁, O₂, and O₃) on the V₂O₅(001) surface. Molecular hydrogen is predicted to spontaneously form at the hole site on the V₂O₅(001) surface. Additionally, the activation barrier for the dissociation of hydrogen on V-doped Mg(0001) surface is 0.20 eV, which is only <FRACTION><NUM>1</NUM><DEN>5</DEN></FRACTION> of that on pure Mg(0001) surface. Our results indicate that oxygen sites on the V₂O₅(001) surface and the V dopant in Mg may be important facilitators for dehydrogenation and rehydrogenation, respectively. The understanding gained here will aid in the rational design and development of Mg-based hydrogen storage materials. [ABSTRACT FROM AUTHOR]