Effects of Fluorine and Titanium Codoping on Hydrogen Desorption Properties of Hydride NaMgH3

Abstract:

The intrinsic mechanism of effects of Ti and F ions codoping on the dehydrogenating properties of the NaMgH3 hydrides was investigated by means of a plane-wave pseudopotential (PW-PP) method based on the density functional theory (DFT). The doped F ion replace some of hydrogen in the hydride to increase the hydrogen desorption properties of the system and subsequently Ti ions substitute for some of Na in Na4Mg4H11F. The electronic structure analysis shows that the strong interactions between H and metals (especially H-1s and Ti-3d) result in a split of the hydrogen energy level near the Fermi energy (EF) level. One part shifts to the left apart from the EF level while the other part shifts to the right over the EF level. The stability of hydrogen in the doped hydride is decreased compared with that in the NaMgH3 hydride without doping, thus improving the hydrogen desorption performance of the hydride

Key words:hydrogen storage material; Ti doping; F doping; reaction enthalpy; formation enthalpy