Theoretical Study of Hydrogen Dissociation on the TiAl$_{3}$ Surface

In order to better understand the catalytic role played by Ti in enhancing the reaction kinetics of sodium alanate, we present a first-principles investigation of hydrogen dissociation and adsorption on the pure Al surface as well as on the Ti doped surface with a local alloy composition of TiAl$_{3. }$ The most energetically favorable location for Ti near the surface is identified. It is found that the presence of Ti promotes H adsorption on the surface with the H atom sitting on top of an Al atom. The binding between Ti and Al modifies the surface charge distribution near the adsorption site and facilitates the adsorption process. The potential energy surface for H$_{2}$ dissociation over both pure Al and the alloy surfaces are also discussed.