DFT studies on doping effect of Al12X: adsorption and dissociation of H2O on Al12X clusters

The adsorption and reaction of H2O molecule on neutral X-centered icosahedronal Al12X clusters (X = Al, Mg, Zn, Ga, Ni, Fe, B, C, Si, P) were investigated by PW91, PBE, and PWC methods. Reaction energies and reaction barriers were determined. The spin states and the doped atoms have important influences on the Al12X geometries, density, electronic properties, and energy density of reaction between Al12X with a single H2O molecule. The energies of the neutral X-centered Al12X are lower than that of surface X-replaced Al12X with the exception of Al12Mg. The H2O dissociation on the Al12X (X = Mg, Zn, Ga, Ni, Fe) clusters have relatively low activation barriers, but large activation barriers for Al12X (X = B, C, Si, P). The activation barrier of water dissociation on the singlet Al12Fe cluster is the lowest, whereas the highest barrier is with the Al12C. The reaction of H2O with Al12Fe is the most exothermic. The center-Fe atom can move out to the surface after the adsorption and dissociation of H2O with an energy barrier of 172 kJ/mol. The results showed that the water dissociation on the Al12X cluster can be tuned by controllable X doping.