The H2 adsorption and dissociation on Pdn（n=4,6,13,19,55）clusters were studied with GGA-DFT.The adsorption energies|Ead|decrease from 0.81,0.67,0.64 to 0.45e V for H2 adsorbed on the Pdn（n=4,6,13,19）,and increase to 0.51e V on the Pd55.Compared adsorption energies with energy barriers,the H2 dissociation is energetically favorable.Energy barriers of the H2 dissociation decrease from 0.41,0.40 to 0.058e V on the Pdn（n=4,6,13）and increase to 0.18 and 0.20e V on the Pdn（n=19,55）.The Hirshfeld charge revealed that charge-transfer from Pdn to H2 increases upon adsorption-dissociation.PDOS showed that the s-band of H2 shifts toward Fermi level and d-band of the Pd4-2H complexes is more delocalized upon H2 dissociation.Present results showed structure sensitivity of the H2 adsorption-dissociation on the Pdn clusters due to inherent size changes.
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