In this study, molecular and atomic adsorption energies and the total density of states (DOS) of hydrogen at the on-top, bridge, and hollow positions of face-centered cubic (FCC) (100) and (111) surfaces of metallic platinum were investigated by density functional theory (DFT) calculations. The results of DOS showed that there was a higher interaction between hydrogen molecules and the FCC (111) surface than the FCC (100) surface of metallic platinum. Also, the intensity of the antibonding orbital of the bridge position was higher than that of the other two positions on the FCC (100) surface, which shows that the hydrogen molecule in the bridge position was ready to be dissociated into hydrogen atoms. In addition, the intensities of the antibonding orbital of hollow and bridge positions were higher than that of the on-top position on the FCC (111) surface, indicating that the hydrogen molecule in hollow and bridge positions was dissociated into hydrogen atoms. The results showed that a comparison between the activation energy barrier (ΔEads), calculated by the Lennard-Jones potential, and molecular adsorption energy could determine whether the hydrogen molecule was dissociated on the surface. Accordingly, if the activation energy barrier (ΔEads) is higher than the molecular adsorption energy, the probability that the hydrogen molecule will dissociate on the surface is very low.

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