Catalytic properties of monometallic and bimetallic palladium and rhodium nanoparticles obtained in reverse micellar systems

Abstract

In this paper, the results of the adsorption and catalytic properties of the mono- and bimetallic palladium and rhodium nanoparticles (0.7–6.5 nm) impregnated on γ-Al2O3 were presented. Metal nanoparticles were obtained in reverse micelles by two reduction methods: radiation-chemical and chemical reduction of ions. Three types of bimetallic nanoparticles Rhcore/Pdshell, Pdcore/Rhshell and substitution alloy Rh-Pd were obtained. The isotope exchange H2+D2⇄2HD and the conversion ortho-H2⇄para-H2 reactions were used as model catalytic processes. It was found that with increasing ω=[H2O]/[surfactant] in addition to increasing the size of the formed particles, also the ratio of particle sizes in a micellar system changes, and in systems with a high value ω, the formation of fine particles is observed. The BMNPs of Rhcore/Pdshell type, showing a synergistic effect in the catalytic properties of reactions involving molecular hydrogen, were obtained [Ks(Rhcore/Pdshell)>4 Ks (Rh or Pd)]. The dependence of the catalytic activity for Rh and Pd NPs on their sizes was obtained. The catalytic activity of the NPs increases with their diameters in the studied range of sizes. The phenomenon of aggregation (sintering) of Rh NPs at a temperature of 800°C was observed. Reflected attempt to compare the optical absorption spectra with the type of nanoparticles.

Keywords

• catalysis
• deuterium
• nanoparticle
• palladium
• rhodium