Theoretical Studies For Catalytic Properties Of Transition Metal Clusters With The Coinage Metals

Bulk materials of coinage metal exhibit inertness to be used as currency,but corresponding metal clusters present chemical active.The atom on the cluster is substituted with other transition-metal atoms to obtain bimetallic cluster,which can alter chemical active because of interaction between heteroatom and host atoms.To obtain catalytic properties of transition metal clusters with the coinage metal,we have investigated adsorption configuration of molecule on the cluster,electronic transfer in the adsorption system,reaction mechanism and influence of heteroatom on the catalytic properties via density-functional calculations.The main contens are illustrated as follow:1.The reaction mechanism of CO oxidation on the Cu13 cluster has been explored.The results indicated Cu13 has high catalytic activity for CO oxidation,especially for O2 adsorption on the cluster.We have considered five possible reaction channels as function of Eley-Rideal(ER)and Langmuir-Hinshelwood(LH)mechanisms and analyzed the adsorption configuration,adsorption energy,Mulliken charge and orbitals in the reaction.There are two pathways are less possible,in which the activity energy of generation and decomposition for intermediates are larger,45.40 and 99.78 kJ/mol,respectively.2.The catalytic properties of the Cu13 cluster and its bimetallic clusters for N2O decomposition have been investigated.The results indicate N2O decomposition on the copper cluster with icosahedral configuration is more prone to be along the ER channel,in which the structure of the Cu13 is obvious relaxtion.The core atoms in the bimetallic cluster can lower repulsive force between the core atom and copper shell to keep configuration,but do not weaken the catalytic properties and promote productions desorption.These clusters have high active for N2O decomposition,especially the Ni@Cu12.3.The active of the Au19Pd and Au19Pt for N2O decomposition have been studied,and compare with other corresponding periodic systems.The results show the configurations of Pd-and Pt-doped gold clusters are stable tetrahedral pyramid.The LH pathway can be more optimized for decomposition of the N20 on the doped gold cluster,in which the heteroatom is on the surface of cluster.It is found that the active of the doped gold clusters have higher for reaction in comparison with periodic system in the reference.And also the structure of the catalyst and a different active atom can obviously influence the activity of substrate in the reaction.4.The CO oxidation on the doped gold clusters Au19Pd and Au19Pt,in which the impurity atom is on the surface,edge or vertex of the cluster,have been investigated.The calculation results present different active atom on the different site of the catalyst can have effect on the activity of the substrate.And also the activity of the catalyst can be weakened because of steric hindrance in the reaction.