Novel yolk–shell-structured Fe3O4@γ-AlOOH nanocomposite modified with Pd nanoparticles as a recyclable catalyst with excellent catalytic activity

A novel yolk–shell-structured material (Fe 3 O 4 @γ-AlOOH-YSMs) with hierarchical γ-AlOOH flakes as the mesoporous shell and Fe 3 O 4 nanoparticles (NPs) in the hollow core was prepared by using Fe 3 O 4 @SiO 2 NPs as the seeds as well as NaAlO 2 and urea as the precursor. The prepared Fe 3 O 4 @γ-AlOOH-YSMs were used as a catalyst support for fabricating a Pd/Fe 3 O 4 @γ-AlOOH-YSMs nanocatalyst with no obvious aggregation of the Pd NPs. The Pd/Fe 3 O 4 @γ-AlOOH-YSMs nanocatalyst was utilized for the catalytic reduction of the widely used and highly toxic 4-nitrophenol, rhodamine B, methylene blue, and methyl orange; and showed excellent catalytic activity as compared with other noble-metal-based catalysts. Furthermore, the Pd/Fe 3 O 4 @γ-AlOOH-YSMs nanocatalyst also can be easily separated from the reaction mixture and reused for at least ten times without any obvious decrease in the catalytic activity, indicating its reusability and stability.