Abstract
Platinum group metals (PGMs) are widely used for exhaust emission abatement. Sintering during high-temperature emission control conditions decreases noble metal utilization efficiency. Efficient use of scarce noble metals requires sinter-resistant catalysts. Here, we extend an approach to synthesize catalysts consisting of platinum nanoparticles encapsulated in a mixture of cerium and aluminum oxides (Pt@Al2O3–CeO2). We tested the activity of this catalyst toward carbon monoxide, propene, and propane oxidation, chosen as model oxidation reactions for emission control catalysts. Pt@Al2O3–CeO2 catalysts demonstrated similar activity and stability upon aging as the comparison system without ceria, Pt@Al2O3, while maintaining small Pt nanoparticles and ceria crystallites. Additionally, we studied the influence of various thermal treatments on the carbon monoxide (CO) oxidation activity and determined that a steam treatment can activate the low-temperature CO oxidation activity of Pt@Al2O3–CeO2. Scanning transmission electron microscope–energy-dispersive X-ray spectroscopy (STEM–EDS) analysis revealed that thermal treatments led to the colocation of Pt and CeO2, and temperature-programmed reduction analysis revealed that the steam treatment specifically enhanced CO oxidation activity through surface reduction of the CeO2. In summary, we demonstrate the versatility of this encapsulation approach to generate mixed metal-oxide supports with improved metal–support interactions without hindering the nanoparticle stability.
