First-principles predictions of potential hydrogen storage materials: Nanosized Ti(core)/Mg(shell) hydrides

作者：Tao S X^*; Notten P H L; van Santen R A; Jansen A P J

来源：Physical Review B, 2011, 83(19): 195403.

DOI：10.1103/PhysRevB.83.195403

MgH(2) is one of the most promising hydrogen storage materials. However MgH(2) is thermodynamicly too stable, leading to a too high desorption temperature of 300 degrees C at atmospheric pressure, which is a major impediment for practical applications. In this study, aiming to tune the thermodynamic stability of the MgH(2), nanosized two-dimensional Mg/Ti/Mg sandwich and three-dimensional Ti(core)/Mg(shell) hydrides have been investigated by using density functional theory calculations. For both structures, four types of hydrogen atoms can be distinguished: on the surface of the Mg (H(surf)), within the Mg (H(Mg)), at the Mg/Ti interface (H(MgTi)), and within the Ti (H(Ti)). For the dehydrogenation reaction, the hydrogen desorption from the hydride is in the order H(surf), H(Mg), H(MgTi), H(Ti). The desorption energy of H(surf) is unexpectedly high. As expected, due to the well-preserved fluorite structure of the partially hydrogenated hydride, the desorption energy of H(Mg) is significantly lower than that of bulk rutile MgH(2). The further desorption of H(MgTi) and H(Ti) becomes more difficult due to the strong Ti-H bonding. We propose that partial hydrogenation without adsorption of H(surf) and partial dehydrogenation without desorption of H(MgTi) and H(Ti) would keep the fluorite symmetry with its favorable thermodynamics. The reversible hydrogen capacity (H(Mg)) of the Mg/Ti/Mg sandwich structure is low, whereas the reversible hydrogen capacity of the Ti(core)/Mg(shell) is calculated to be reasonable high. Our results predicted Ti(core)/Mg(shell) structures are potential useful materials for hydrogen storage application.

• 出版日期2011-5-3