Al12X (X = Ni, Pd, Pt, Ti, and Zr) Clusters: Promising Low-Cost and High-Activity Catalysts for CO Oxidation

CO oxidation on the surface of various Al12X (X = Ni, Pd, Pt, Ti, and Zr) clusters is investigated by density functional theory (DFT) calculations. The molecular structures and surface-adsorbate interaction energies of CO and O-2 on the Al12X (X = Ni, Pd, Pt, Ti, and Zr) cluster surfaces are predicted. The frontier orbital picture (FOP) successfully predicted the cluster-CO or cluster-O-2 ground-state configurations for all Al12X clusters. The calculated results indicate that the CO oxidation reaction is sensitive to the properties of different transition metals, and the order of activation barrier for CO reaction with molecular O-2 and CO reaction with the adsorbed oxygen atom is different for Al12X (X = Ni, Pd, Pt) clusters. A trimolecular Langmuir-Hinshelwood (LH) mechanism with two coadsorbed CO molecules and one coadsorbed O-2 molecule is proposed, which will lead to the spontaneous formation (due to extremely low energy barrier) of two CO2 molecules as product. The calculated results show that the order of activation barrier for two CO molecules oxidation on the Al12X clusters is Al12Ti (0.08 eV) < Al12Zr (0.13 eV) < Al12Pt (0.19 eV) < Al12Ni (0.22 eV) < Al12Pd (0.24 eV). The lower calculated barrier energies of two CO oxidations on Al12X indicate that CO could be efficiently oxidized at low temperature on Al12X clusters. These findings enrich the applications of Al-based materials to the high-activity catalytic field.