Dispersion and Stability Mechanism of Pt Nanoparticles on Transition-Metal Oxides

The heterogeneous catalysts of Pt/transition-metal oxides are typically synthesized through calcination at 500℃, and Pt nanoparticles are uniformly and highly dispersed when hydrogen peroxide (H 2 O 2 ) is applied before calcination. The influence of H 2 O 2 on the dispersion and the stability of Pt nanoparticles on titania-incorporated fumed silica (Pt/Ti-FS) supports was examined using x-ray absorption fine structure (XAFS) measurements at the Pt L 3 - and Ti K-edges as well as density functional theory (DFT) calculations. The local structural and chemical properties around Pt and Ti atoms of Pt/Ti-FS with and without H 2 O 2 treatment were monitored using in-situ XAFS during heating from room temperature to 500℃. XAFS revealed that the Pt nanoparticles of H 2 O 2 -Pt/Ti-FS are highly stable and that the Ti atoms of H 2 O 2 -Pt/Ti-FS support form into a distorted-anatase TiO 2 . DFT calculations showed that Pt atoms bond more stably to oxidized-TiO 2 surfaces than they do to bare- and reduced-TiO 2 surfaces. XAFS measurements and DFT calculations clarified that the presence of extra oxygen atoms due to the H 2 O 2 treatment plays a critical role in the strong bonding of Pt atoms to TiO 2 surfaces.