Design of Enhanced Catalysts by Coupling of Noble Metals (Au,Ag) with Semiconductor SnO2 for Catalytic Reduction of 4-Nitrophenol

The reduction of 4-nitrophenol (Nip) into 4-aminophenol (Amp) by NaBH4, which is catalyzed by both binary and ternary yolk-shell noble-metal/SnO2 heterostructures, is reported. The binary heterostructures contain individual Au or Ag nanoparticles (NPs) and the ternary heterostructures contain both Au and Ag NPs. The Au@SnO2 yolk-shell NPs are synthesized via a silica seeds-mediated hydrothermal method. Subsequently, the Au@SnO2@Ag and Au@SnO2@Au yolk-shell-shell (YSS) NPs are synthesized, whereby SnO2 is located between the Au and Ag NPs. The morphology, composition, and optical properties of the as-prepared samples are analyzed. For the binary heterostructures, the rate of the reduction reaction increases with decreasing particle size. The catalytic results demonstrate the synergistic effect of Au and Ag in the ternary metal-semiconductor heterostructures, which is beneficial to the catalytic reduction of Nip into Amp. Both the binary and ternary heterostructures exhibit significantly better catalytic performances than the corresponding bare Au and Ag NPs. It is envisaged that the current synthesized strategy will promote further interest in the field of bimetal NP-based catalysis.