Synthesis of Pd(0) Nanoparticles in TiO2–SiO2 Xerogel

Resumo

Pd/TiO₂–SiO₂ xerogels containing 0.15–0.75 wt % palladium are prepared from Pd(NO₃)₂ · 2H₂O solutions in a mixture of tetrabutoxytitanium (TBT) and tetraethoxysilane (TEOS) in a desiccator under acetic acid–water vapors in the batch mode at 20°С followed by drying and calcination of the material at 850°С. IR spectroscopy showed that the presence of Pd(NO₃)₂ · 2H₂O has no effect on the amount of newly formed Ti–O–Si bonds in the double oxide TiO₂–SiO₂ over the range of salt concentrations studied. X-ray powder diffraction showed that palladium present in the xerogel calcined at 850°С is in the form of Pd(0) nanoparticles. The electron-microscopic morphology study showed that the items prepared (Pd(0) nanoparticles) had near-spherical shapes; their sizes fell in the range 20–230 nm. A means for varying Pd(0) nanoparticle size in the material is to vary the palladium(II) salt concentration at the dissolution stage.