Synthesis of a magnetically heatable ceria–supported ruthenium catalyst via deposition of nanocrystalline ceria on silica-coated magnetic iron–oxide nanoparticles

ABSTRACT We report the synthesis of a ceria-based catalyst support containing embedded magnetic iron–oxide nanoparticles (IONPs) that enable heating under a high-frequency alternating magnetic field. The ≈11 nm IONPs, synthesized by co-precipitation of Fe 2+ /Fe 3+ ions at room temperature, were coarsened to ≈18 nm through subsequent hydrothermal treatment at 120 °C and then coated with a ≈2 nm silica layer. The catalyst support was prepared by depositing nanocrystalline ceria (CeO 2 ) onto the IONPs via controlled precipitation of Ce 3+ ions in the presence of hexamethylenetetramine (HMTA) in aqueous suspension. When deposited directly on the iron oxide, ceria formed small agglomerates of ≈10 nm octahedral nanocrystallites, whereas deposition on silica-coated IONPs produced a homogeneous 3–6 nm-thick shell composed of ≈3 nm globular crystallites. Special attention was given to elucidating the mechanism of shell formation. The magnetic catalyst was obtained by precipitating Ru nanoparticles (1–2 nm) onto the ceria support. Morpho-structural characterization was performed by XRD, TEM, and aberration-corrected STEM. Static and dynamic magnetization measurements at room temperature were used to assess the magnetic and heating performance. At low field amplitudes (