Hydrogen adsorption and dissociation on small Al_nA_u clusters: an electronic structure density functional study

摘要

We present density functional calculations of H2 adsorption and dissociation on small-sized AlnAu clusters for n = 1?13. The growth pattern for AlnAu (n = 2?5, 7, 12, 13) clusters is Au atom occupying a peripheral position of Al_n clusters. And the growth pattern for Al_nAu (n = 6 and 10) clusters is Au-substituted Al_(n+1) clusters. It is found that the Au atom substituted the surface atom of Aln+1 cluster and occupies a peripheral position. H2 is easily physically absorbed on the top Au atom of AlnAu clusters with an end-on orientation rather than side-on orientation because of the more effective orbital overlap in the end-on orientation. The reaction of Al_nAu with H_2 would produce Al_nAuH_2 because of large exothermic energy changes and relatively small activation energies especially for Al_3Au and Al_7Au, which might serve as highly efficient and low-cost catalysts for hydrogen dissociation.