Highly Dispersed Pt Species with Excellent Stability and Catalytic Performance by Reducing a Perovskite-Type Oxide Precursor for CO Oxidation

摘要

A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCo_(1-x)Pt_xO_3/SiO_2( x = 0.03, 0.05, 0.07, 0.09, and 0.10) were prepared through a simple method of citrate acid complexation combined with impregnation. In a nanocrystallite of LaCo_(1-x)Pt_xO_3, ions of lanthanum, cobalt, and platinum are evenly mixed at the atomic level and confined within the nanocrystallite. In the reduction process, platinum ions were reduced and migrated onto the surface of the nanocrystallite, and the platinum should be highly dispersed owing to the even mixing of the platinum ions in the precursor. When x = 0.05 or lower, the highest dispersion of Pt could be achieved. The highly dispersed Pt is stable, because of the strong interaction between Pt atoms and the support. The catalysts were characterized by BET surface area, temperature-programmed reduction, X-ray diff raction, transmission electron microscopy, CO temperatureprogrammed desorption, and turnover frequency. Compared with general precious metal Pt catalysts, the LaCo_(0.95)Pt_(0.05)O _3/SiO_2 catalyst exhibited better activity for CO oxidation, and it maintained stability at a high temperature of 400 ℃ for 250h with complete CO conversion.