The surface Pt species and adsorbed oxygen on the Pt/ZrO 2 catalyst were successfully modulated by altering the preparation methods, resulting in distinct catalytic behaviors for CO, n-heptane, and toluene oxidation. The Pt/ZrO 2 catalyst was initially prepared via wetness impregnation and subsequently reduced in an H 2 atmosphere to obtain the Pt/ZrO 2 -R catalyst. In contrast, the Pt/ZrO 2 -E catalyst was synthesized using ethanol solvent (also serving as a reducing agent) instead of water during wetness impregnation. Moreover, the pre-prepared Pt nanoparticles were loaded onto the ZrO 2 surface using polyvinylpyrrolidine (as a protective and structure directing agent) dissolved in ethanol solvent to fabricate the Pt/ZrO 2 -EP catalyst. Among these catalysts, the Pt/ZrO 2 -R exhibits superior catalytic activity towards CO oxidation due to its abundant metallic Pt species. It is found that activity of Pt/ZrO 2 catalyst for n-heptane oxidation is positively correlated with its surface adsorbed oxygen concentration, thus the highest activity is achieved over the Pt/ZrO 2 -EP catalyst possessing a higher concentration of surface adsorbed oxygen species. Unlike CO and n-heptane oxidation, toluene oxidation activity is affected by multiple factors, it is primarily promoted by synergistic catalysis between metallic Pt species (Pt 0 ) and surface adsorbed oxygen species over the Pt/ZrO 2 -EP catalyst. Our preliminary findings underscore that precise modulation of sensitive active sites on surfaces plays a critical role in specific catalytic reactions.
A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCo 1− x Pt x O 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 x O 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 diffraction, transmission electron microscopy, CO temperature-programmed 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 °C for 250 h with complete CO conversion.
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