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Polyvinyl alcohol (PVA) has been shown to interact with platinum ions by manipulating the reaction time. It was interestingly found that the improved low-temperature oxidation performance of Pt-based catalysts in promoting the conversion of CO/C3H6/NO was mainly contributed to by a higher content of metallic platinum species, accompanied by relatively smaller platinum nanoparticle size. Besides, DTA and in situ DRIFTs of the un-roasted catalysts showed that an appropriate reaction time (10 h) between the platinum ions and polyvinyl alcohol resulted in a strong electronic intensity of the platinum. Both these factors led to a greater formation of formate species and the lowest light-off temperature of CO (176 °C), C3H6 (187 °C), and NO (214 °C). This simple method involving tuning the interaction of polymer and metal ions would be positive for optimizing the electronic state and size efffect of metals in catalysis. [ABSTRACT FROM AUTHOR]

For diesel oxidation catalyst (DOC), the sintering and oxidation of active Pt0 nanoparticles leads to severe deactivation during long-term operating condition. Here, we have synthesized SiO 2 -modified Pt/SiO 2 -Al 2 O 3 (Pt-SiAl@Si) catalysts, and this silica coating layer not only can inhibit the migration of precious metals through physical isolation, but also restrain Pt0 oxidation by interfacial electron interaction between Pt and acid sites (Si-OH-Al). Before and after hydrothermal aging, the maximum NO conversion of Pt-SiAl@Si decreased slightly by 5%, showing excellent durability. TEM and CO chemisorption unveiled that no obvious differences in Pt size between fresh and aged Pt-SiAl@Si. 1H NMR and NH 3 -DRIFTS confirmed that Pt-SiAl@Si possessed more Brönsted acid sites (Si-OH-Al). And the Pt−acid sites interface caused more active Pt0 by the electronic effect. This bifunctional overcoating allows a wide application in other catalytic materials for various reactions. [Display omitted] • The SiO 2 overlayer of Pt-SiAl@Si is bifunctional. • SiO 2 shell as a physical barrier has an ability to retard sintering of Pt nanoparticles. • Pt-acid sites interfaces arising from interaction between SiO 2 shell and support enhanced the oxidation-resistance of Pt0. • The increased acidity of catalyst promoted the fast desorption and decomposition of nitrate species, facilitating NO oxidation. [ABSTRACT FROM AUTHOR]