摘要
Au@Fe 3 O 4 yolk-shell nanocatalysts based on the thermal decomposition of iron pentacarbonyl in the presence of 2.5-10-nm Au core nanoparticles were successfully fabricated for the catalytic reduction of nitroarenes. The particle sizes of the Au@Fe 3 O 4 nanostructures were in the range 8-15 nm, with Fe 3 O 4 shell layer thicknesses of 2.0-2.4 nm. The Fe 3 O 4 layer not only can form a magnetic shell for recovery but also enables the protection of the catalytic activity of the Au core nanoparticles toward the reduction of nitrobenzene derivatives including 2-nitrophenol, 4-nitrophenol, 4-nitrotoluene, and 1-chloro-4-nitrobenzene in the presence of NaBH 4 . The catalytic performance of Au@Fe 3 O 4 is highly dependent on the particle size of the Au core materials and the substituent groups of the nitroarenes. The reduction rates of nitroarenes with electron-withdrawing groups were found to be 2.3-2.6 times higher than those of nitroarenes with electron-donating groups. In addition, the reduction of nitroarenes by the Au@Fe 3 O 4 yolk-shell nanocatalysts was found to be a surface-mediated reaction, and the relationship between the reduction rate and the initial NaBH 4 concentration was found to follow Langmuir-Hinshelwood kinetics. Moreover, the yolk-shell nanoparticles showed good separation ability and reusability, as they could be repeatedly applied for the nearly complete reductions of 4-nitrophenol and 1-chloro-4-nitrobenzene for at least five successive cycles. These unique properties make Au@Fe 3 O 4 nanocatalysts an ideal platform for tailoring yolk-shell nanoreactors with various active materials and also for studying various heterogeneous catalytic processes.