Synthesis of Pt/SiO2 Catalyst Nanoparticles from a Continuous Aerosol Process using Novel Cyclo-octadienylplatinum Precursors

Investigations on the metal-organic (MO)CVD of platinum nanoparticles on spherical, chemical vapor synthesis (CVS)-produced SiO2 substrates are discussed in this paper. Commercially available methylcyclopentadienyl trimethyl platinum (MeCpPtMe3) (1) and three newly synthesized cyclooctadienyl platinum precursors are chosen and tested during a continuous CVD/CVS process. The synthesis of this new class of stable, halogen-free precursors for atmospheric pressure (AP)CVD is presented. The complexes [PtMe2(R-COD)], where R=Et (2a), Bu-n (2b), and Bu-i (2c), are shown to be highly suitable for the preparation of platinum nanoparticles. The precursors are characterized and their thermal properties are studied by thermogravimetric analysis (TGA) and infrared (IR). Investigations of the precursor decomposition mechanism, the effect of oxygen, and the autocatalytic effect during CVD are also carried out. Finally, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses prove that continuous CVS of gas-borne support particles combined with MOCVD of these newly synthesized platinum precursors gives ordered, defined platinum nanocatalysts with high dispersion and narrow size distribution (2-3nm).