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 °C, and Pt nanoparticles are uniformly and highly dispersed when hydrogen peroxide (HO) is applied before calcination. The influence of HO 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 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 HO treatment were monitored using in-situ XAFS during heating from room temperature to 500 °C. XAFS revealed that the Pt nanoparticles of HO-Pt/Ti-FS are highly stable and that the Ti atoms of HO-Pt/Ti-FS support form into a distorted-anatase TiO. DFT calculations showed that Pt atoms bond more stably to oxidized-TiO surfaces than they do to bare- and reduced-TiO surfaces. XAFS measurements and DFT calculations clarified that the presence of extra oxygen atoms due to the HO treatment plays a critical role in the strong bonding of Pt atoms to TiO surfaces.