Cluster Properties of Au19Pt and Selective Hydrogenation Mechanism of Cinnamaldehyde on Au19Pt Cluster Surface

Structural stability, thermodynamic stability and chemical reactivity of the bimetallic Au19Pt clusters were investigated based on the framework of the relativistic density functional theory. It was calculated that Au19Pt-V cluster was chemically more active than Au19Pt-S and Au19Pt-E clusters but thermodynamically less stable. To explore the most stable adsorption configuration, the adsorption behavior of a cinnamaldehyde on three types of bimetallic Au19Pt cluster was studied via analyzing the adsorption energy and Mulliken charge. The calculation results indicate that a cinnamaldehyde molecule is preferably adsorbed on Pt site in Au19Pt-V cluster with C = C, in which the adsorption configuration is the most stable. In that condition, the adsorption energy and the amount of charge transfer are maximum. Moreover, 6 possible mechanisms were investigated of three kinds of selective hydrogenation reaction (1,2-additive reaction, 3,4-additive reaction and 1,4-conjugate additive reaction) of cinnamaldehyde on Au19Pt-V cluster, on the basis of the most stable adsorption configuration. Compared with the reaction energy, activation energy and configuration change of each elementary steps, it suggests that the most favorable way of the cinnamaldehyde on the Au19Pt-V cluster would be through 3,4-additive reaction (mechanism C). The specific reaction pathway involved a C3 atom preferentially hydrogenating to generate MS3 intermediate, another H atom added to intermediate to take shape C4-H bond. Then the final product phenylpropyl aldehyde is forming through the transition state TS34.