Comparative Investigation on the Adsorption Properties of Precious Metal Clusters toward NO: A Density Functional Study

Abstract

The adsorption properties of precious metal clusters such as Rh, Pd, Ag, Ir, Pt, and Au toward NO were systematically investigated using the density functional calculations. It was found that the most energetically stable adsorption state of NO on the tetrahedral M4 clusters was found to be the NO/Ir4 system. The ability of the precious metal clusters to activate the N−O bond was also discussed mainly from a geometric point of view. The entire linear behavior of the elongation of the N−O bond of NO molecules adsorbed on M4 clusters was observed with increasing values of the molecular charge on the NO molecules, which suggests the back-donation of an electron to the 2π* orbital of the NO molecules. The substantial elongation of the N−O bond was found on the NO/Ir4 system, which was nearly equal to that on the NO/Rh4 systems. These results indicate that the Ir cluster has the best properties for the adsorption and activation of NO.