Bimetallic nanoparticles (Ru-Re, Ru-Pt) are considered as effective catalyst in combustion of methane and propane. They are currently being tested in reaction of catalytic oxidation of soot, which is important due to the common problem of air pollution. The properties of catalysts strongly depend on the morphology, structure and dispersion of nanoparticles, and all this information, with sufficient spatial and energy resolution, can be obtained by Transmission Electron Microscopy.
Nanoparticles were synthesized by the microwave assisted polyol approach, with ethylene glycol used as a solvent and reducing agent and RuCl3, (NH4)2(PtCl6) and NH4ReO4 used as metal precursors, and deposited on oxide supports (γ-Al2O3 and TiO2, both rutile and anatase phase). TEM observations were conducted on an S/TEM TITAN 80-300 microscope equipped with EDAX EDS spectrometer. STEM images were collected with a 24.5-mrad probe semi-angle and recorded by HAADF detector at 47–200 mrad range.
Our research has proved that Ru-Re and Ru-Pt catalysts supported on γ-Al2O3 and TiO2 can be effectively prepared in a simple, one-step process. We showed that morphology and microstructure of bimetallic nanoparticles (Ru-Re and Ru-Pt) depend on the used oxide support. The vast majority of Ru-Re and Ru-Pt nanoparticles deposited on γ-Al2O3 had a round shape, with no apparent tendencies for agglomeration. Nanoparticles, had been deposited on rutile and anatase substrates, formed elongated systems consisting of several smaller crystallites around TiO2 crystals. This kind of behavior on rutile was present both with lower (2%-0,8%) and higher (5%-2%) loading of metals. As for anatase, a 5% -2% metal load was required to observe this phenomenon. Based on microscopic observations, we can deduce that catalysts supported on γ-Al2O3 are characterized by higher catalytic activity, due to the higher share of atoms on the surface of nanoparticles compared to all atoms forming the nanoparticle.
This work is carried out within the POWROTY/REINTEGRATION programme of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund (Grant No. POIR.04.04.00-00-5F33/18-00) and Najlepsi z Najlepszych 4.0 programme of the Polish Ministry od Science and Higher Education co-financed by the European Union under the European Social Fund.