Catalytic effect of Ti and Ni on dehydrogenation of AlH3: A first principles investigation

•Ni doped in bulk and on the surface of AlH3 are unfavourable comparing to Ti.•Ti and Ni prefer to substitute for Al atom in both the bulk and surface doped systems.•Ti improves the dissociation properties of AlH3 by weakening the interactions between Al and H atoms, but the catalytic effect is weaker if Ti substitutes for Al than its interstitial doping. Ab initio calculations were performed for the M-doped (M=Ti or Ni) AlH3 to investigate influence of dopants Ti and Ni on the dehydrogenation properties of AlH3. It was found that Ti and Ni prefer to substitute for Al atom in both the bulk phase and the slab surface. However a large amount of energy was needed for Ni to dope into AlH3 making that Ni might not a suitable catalyst for AlH3. Mechanisms that Ti improved the dehydrogenation properties of AlH3 were clarified. Ti greatly decreased the dehydrogenation energy of AlH3 by weakening the interaction between Al and H atoms, its influence on the dehydrogenation of AlH3 was however sensitive to the occupation behavior. The calculations indicated that the catalytic effect of Ti was weaker if Ti substitutes for Al than its interstitial occupation.