Design of a core–shell Pt–SiO2 catalyst in a reverse microemulsion system: Distinctive kinetics on CO oxidation at low temperature

• Published in: Journal of catalysis Vol. 340; pp. 368 - 375
• Main Authors: Almana, Noor, Phivilay, Somphonh Peter, Laveille, Paco, Hedhili, Mohamed N., Fornasiero, Paolo, Takanabe, Kazuhiro, Basset, Jean-Marie
• Format: Journal Article
• Language: English
• Published: San Diego Elsevier Inc 01.08.2016; Elsevier BV
• Subjects: ammonia; carbon monoxide; catalysts; CO oxidation; Core–shell; Diffusion; emulsions; hydrolysis; Kinetic study; nanocrystals; nanoparticles; oxidation; Pt@SiO2; silica; temperature; Kinetic study; Core–shell; Pt@SiO2; Diffusion; CO oxidation
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2016.06.002

[Display omitted] •Controlled synthesis of a core–shell structure is established to yield various Pt@SiO2 samples.•Turnover frequency for CO oxidation is higher for Pt@SiO2 core–shell catalysts than for Pt/SiO2-supported catalysts.•The SiO2 shell plausibly functions as a membrane leading to a distinctive gas concentration at the Pt core. The mechanism of formation of Pt@SiO2 as a model of core–shell nanoparticles via water-in-oil reverse microemulsions was studied in detail. By controlling the time of growth of Pt precursors, Pt(OH)x, after hydrolysis in NH3 aq. before adding SiO2 precursor (TEOS), Pt nanoparticles with a narrow size distribution were produced, from ultrafine metal nanoparticles (<1nm) to 6nm nanocrystals. Separately, the thickness of SiO2 was controllably synthesized from 1 to 15nm to yield different Pt@SiO2 materials. The Pt@SiO2 core–shell catalysts exhibited a higher rate of CO oxidation by one order of magnitude with a positive order regarding CO pressure. The SiO2 shell did not perturb the Pt chemical nature, but it provided different coverage of CO in steady-state CO oxidation.