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 (O-1, O-2, and O-3) 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 1/5 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. (c) 2008 American Institute of Physics.