Synthesis of Palladium Nanoparticles on the Surface of Cerium(IV) Oxide under the Action of Ultraviolet Radiation and Their Characterization

Abstract

Palladium nanoparticles have been synthesized in an aqueous medium by ultraviolet irradiation using complex palladium oxalate as a precursor. The samples were studied by various laboratory methods, including transmission electron microscopy, X-ray fluorescence analysis, X-ray powder diffraction, X-ray absorption fine structure spectroscopy, and diffuse reflectance infrared spectroscopy with the use of CO probe molecules. The microimages obtained by transmission electron microscopy did not allow us to distinguish Pd nanoparticles from the material of the substrate but do not show any effect of ultraviolet irradiation on the sizes of CeO₂ nanoparticles. The X-ray fluorescence analysis data show the presence of cerium and palladium atoms in the material. X-ray diffraction patterns indicate the presence of phases of cerium dioxide and metallic palladium, while the analysis of the X-ray absorption fine structure spectra beyond the K-edge of palladium shows the presence of the PdO phase in the system. The approximate size of the palladium nanoparticles was estimated by the infrared spectra after the adsorption of CO and is less than 2 nm, which is significantly smaller than the average size of Pd nanoparticles obtained by a similar method without a CeO₂ substrate (1.5–9.5 nm).