Photochemical preparation of poly(N-vinyl-2-pyrrolidone)-stabilized platinum colloids and their deposition on titanium dioxide

Preparation processes for Pt-deposited TiO2 (Pt/TiO2) by the synthesis of Pt nanoparticles and their deposition were pursued by transmission electron microscopy, extended X-ray absorption fine structure, UV-vis spectroscopy, and Fourier transform infrared spectroscopic studies. Colloidal dispersions of Pt particles stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) were photochemically synthesized in aqueous ethanol solution. The average diameter of Pt particles was estimated to be 2.0 +/- 0.5 nm, which was almost unchanged by changing the reducing agent from ethanol to methanol and 2-propanol. The PVP-stabilized Pt particles were distributed over a TiO2 surface only by mixing the Pt colloidal dispersions and TiO2. CO was chemically coordinated on the Pt particles on a TiO2 surface after heat treatment was carried out in an O-2 flow at 673 K to completely remove the residual PVP on Pt/TiO2. Hydrogen reduction at 473 K did not increase the amount of CO adsorbed on Pt sites. The Pt/TiO2 catalyst after the oxidation treatment showed higher activity for CO photooxidation than that obtained for pure TiO2 catalyst. The CO photooxidation rate was not unchanged by the H-2 reduction.