Bimetallic systems of mesoporous ordered silica supports and noble metals nanoparticles

Abstract

This paper describes of preparation and characterization of new bimetallic materials based on platinum/silver, platinum/palladium and palladium/silver systems of nanoparticles supported on mesoporous ordered silica composite. In all investigated materials unusual ammine complexes of noble metals ([Pt (NH3)4]Cl2, [Ag(NH3)2]OH and [Pd(NH3)4]Cl2) were used as nanoparticles sources. Bimetallic materials were synthesized by one-pot procedure or post synthesis modification via impregnation method with metal precursors on surface of mesoporous ordered silica. The obtained materials were characterized by various techniques including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), nitrogen physisorption and FTIR/PAS spectroscopy.Proposed system of noble metal nanoparticles allows determining subtle changes in the interaction between metallic phases and porous carrier with particular emphasis of spectroscopic properties. In the current study, we have attempted to relate the synergistic effect of components for understanding relationships between type of noble metal ammine complexes as metal precursors and final material properties. We found that significant interactions occur between supported metals and relatively inert mesoporous ordered silica. What is more, noble metal crystallites in bimetallic systems exhibit different sizes depending on the kind of metal source. Such a difference in sizes of individual components may be responsible for lack or presence of interactions between metal nanoparticles and solid support. Specific distribution of platinum nanoparticles on the support surface and their very small sizes in Pt,Ag/SBA-15 systems causes intrinsic electron deficiency due to the interactions between a small platinum crystallite and the silica surface. The possible interaction effect between palladium and the silicon atoms was also observed. This indicates that the metal-support effect should be considered during designing and production of new functional materials, models of catalysts and adsorbents.