Confinement of Au, Pd and Pt nanoparticle with reduced sizes: Significant improvement of dispersion degree and catalytic activity

Heterogeneous catalytic reactions are strongly relying on metal-based catalysts due to their outstanding activity. However, the activity of catalysts depends on the size of metal nanoparticles (MNPs). Herein, Pd, Pt and Au NPs were confined in the nanoconfined spaces of template occluded as-made KIT-6 (AK) via facile single-step strategy. The metal precursors are directly inserted into the nanoconfined channels of AK by grinding. Subsequent reduction removes template P123, decompose precursors and reduce MNPs in one step in comparison to multiple ones of traditional strategies. The results demonstrated that the nanoconfined channels between template and silica walls of AK where MNPs locate, MNPs interaction with AK and single-step strategy promote the formation of MNPs with smaller size. The characterization results confirmed uniform MNPs distribution with single metallic state without any metallic oxides. The smaller size of MNPs in catalysts endows excellent catalytic activity and the order of para-nitrophenol (p-NP) reduction to p-aminophenol (p-AP) and methylene blue (MB) to leucomethylene blue (LMB) is AK-Pd > AK-Pt > AK-Au. Also, the reaction rate constant of AK-Pd is much better than AK-Pt and AK-Au catalysts. Moreover, the synthesized catalysts exhibited good reusability and are highly promising for utilization in catalytic reactions.