Tailoring metal-oxide interfaces of oxide-encapsulated Pt/silica hybrid nanocatalysts with enhanced thermal stability

Abstract

We report the fabrication of metal-oxide (m-oxide) hybrid nanocatalysts with oxide encapsulation (Pt/SiO2@m-oxide; m-oxide =TiO2, Nb2O5, Ta2O5, CeO2) using a simple surface-modification chemical process. The synthesized m-oxide hybrid nanocatalysts with oxide encapsulation have two advantages: tailoring the metal-support interaction and achieving higher thermal and chemical stability. Briefly, Pt nanoparticles (NPs) capped with polyvinylpyrrolidone were successfully assembled on functionalized SiO2 via electrostatic interactions, and then an ultrathin layer of m-oxide was coated on the surface. Transmission electron microscopy studies confirmed that the Pt NPs were uniformly dispersed and distributed throughout the surface of the SiO2 with a thin layer of m-oxide. In particular, energy-dispersive X-ray spectroscopy line mapping was employed to ensure the presence of a uniformly coated thin oxide layer of constituent elements. The metal NPs were found well exposed to the outer surface, enabling surface characterization, including chemisorption and X-ray photoelectron spectroscopy. Even after calcination at 600 degrees C, the structure and morphology of the hybrid nanocatalysts remained intact, confirming high thermal stability. We investigated the effect of different types of m-oxide coating, an active support material, on the performance of catalytic activity for CO oxidation for the Pt/SiO2@m-oxide hybrid nanocatalysts with well-exposed Pt nanoparticles. We carried out CO oxidation over the hybrid nanocatalysts and found that metal-oxide interfaces play important roles that influence catalytic activity. Designing such metal-oxide hybrid structures with thin oxide encapsulation represents a critical step in the advancement of model catalytic systems for investigating the metal-support interaction with improved thermal stability.