Catalytic enhancement in dissociation of nitric oxide over rhodium and nickel small-size clusters: A DFT study

We applied density-functional theory (DFT) to investigate the adsorption and dissociation of NO on Rh₁₉ and Ni₁₉ clusters with a double-icosahedral (DI) structure. The transition structures of the NO dissociating on the potential-energy surfaces were derived using the nudged-elastic-band (NEB) method. The adsorption energies of NO molecules on the rhombus-center region of DI clusters are -2.53 eV and -2.78 eV with the N-O bond elongated to 1.33 Å and 1.35 Å, respectively, on Ni ₁₉ and Rh₁₉, compared to 1.16 Å of the gaseous NO counterpart. The barriers to dissociation of N-O on both DI-Rh₁₉ (E_a = 0.24 eV) and DI-Ni₁₉ (E_a = 0.42 eV) clusters are small, indicating that the rhombus-center region of DI metal clusters might activate the scission of the N-O bond. To understand the interaction between these nanocluster catalysts and their adsorbates, we calculated the electronic properties including the local densities of states, orbital evolution of the adsorbates and interaction energies; the results indicate that a profound catalytic behavior for bond scission is observed in this unique rhombus-center region of DI metal-nanoclusters.