Hollow Nitrogen-Doped Carbon Nanocages Encapsulating Pd/Fe3O4 Hybrid Nanoparticles with Superior Catalytic...

Exploring sustainable and highly active catalysts with both excellent catalytic reduction ability and enzyme-like performance is of great significance for environmental remediation and biosensing applications. Herein, we report a facile strategy to construct hollow nitrogen-doped carbon nanocages (NCs) encapsulating well-dispersed Fe3O4 and Pd nanoparticles (NPs) (NCs@Pd/Fe3O4) via a polystyrene (PS)-templated interfacial assembly followed by a single-step thermal conversion treatment under a nitrogen atmosphere. Using PS nanospheres as sacrificial templates, the polypyrrole (PPy) shell serves as the carbon/nitrogen source and coordination layer, while FeOOH nanoneedles and Pd precursors are simultaneously converted into magnetic Fe3O4 and highly crystalline Pd NPs during the annealing process. The resultant NCs@Pd/Fe3O4 nanocages possess a unique hollow architecture, mesoporous shells, abundant nitrogen-doping sites, and a high specific surface area, which facilitate rapid mass transport and provide abundant accessible active sites. Owing to the synergistic effect among the conductive N-doped carbon matrix, the magnetic Fe3O4, and the highly active Pd NPs, the obtained nanocomposite exhibits outstanding catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol, as well as superior peroxidase-like activity. Moreover, the incorporation of Fe3O4 endows the catalyst with convenient magnetic recoverability, enabling efficient separation and stable reusability without significant loss of catalytic performance or structural integrity. This work provides a promising strategy for designing multifunctional, magnetically recyclable hollow nanocatalysts for applications in heterogeneous catalysis and colorimetric biosensing.