First-principles calculations were carried out to study the hydrogenation mechanism of Ti-doped NaH/Al mixture to form NaAlH4 structures, with emphasis on the role of NaH. TiAl3Hx (x=0~16) cluster calculations show that that hydrogenation of TiAl3 experienced a structural evolution in which TiAl3 organizes into a distorted tetrahedral skeleton in TiAl3Hx (x=0~7), but forms a planar T-shape structure in TiAl3Hx (x=10~16), with TiAl3H8 and TiAl3H9 being transition structures between the tetrahedral and planar structures. H2 adsorbs molecularly at the Ti site of TiAl3Hx, and dissociates spontaneously into hydrides when an extra electron was added to the cluster. Further, we found that H2 can molecularly adsorb on the Ti position of TiAl3Hx, and dissociate spontaneously to form hydrides when an extra electron was added to the cluster, simulated as TiAl3Hx supported on the NaH (001) surface. Electronic structure analysis shows that TiAl3Hx gains a partial electron through the hydride transfer from the NaH (001) surface, promoting hydrogenation. The present results suggest a possible mechanism of forming NaAlH4 in the recycling of Ti-doped NaAlH4 as a hydogen storage medium.

First-principles studies on hydride-assisted hydrogenation of Ti-doped NaH/Al to form NaAlH<sub>4</sub>

245th National Meeting (2013)

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First-principles studies on hydride-assisted hydrogenation of Ti-doped NaH/Al to form NaAlH4

First-principles studies on hydride-assisted hydrogenation of Ti-doped NaH/Al to form NaAlH₄