Synergic effects of VLi and Ti doping on hydrogen desorption on LiBH4 (010) surface: A first-principles investigation

Ti-doping and Li-vacancy (VLi) crucially affect the dehydrogenation properties of LiBH4 surface. However, theoretical investigations on individual Ti or VLi could not completely explain experimental observations. In this article, we investigated the synergistic effects of co-existing Ti and VLi on the dehydrogenation properties of LiBH4 (010) surface. Our result shows mutual stabilization between Ti-dopant and Li-vacancy, implying expectable co-existence of Ti and VLi. Thermodynamic destabilization from composite Ti + VLi defect agrees with experiments better than that from single Ti or VLi. The kinetic barrier on Ti + VLi decorated surface also becomes closer to experimental result. Therefore, the co-existing Ti and VLi synergistically and crucially affect the dehydrogenation thermodynamics and kinetics on LiBH4 surface. The electronic structure further reveals strong HH, BB, and TiB bonds as well as weakened BH bond in transition states on Ti + VLi co-existed surface, which is the main factor of low kinetic barrier.