Enhanced catalytic nitrophenol reduction via highly porous hollow silica nanospheres stabilized Au nanoclusters

In this work, we report the synthesis of Au nanoparticles encaged in hollow porous silica nanospheres (Au@HPSNs), which features extremely small Au nanoclusters (-1.3 nm) encapsulated in high specific surface area (-800 m2/g) HPSNs. We used the electrostatic attraction between the anions of poly(acrylic acid) (PAA) and protonated poly(ethylenimine) (PEI) to build the micelles system in an ethanol-water system, which was employed as the templates for deposition of silica to give the core-shell structured PEI-PAA@SiO2. The final materials Au@HPSNs were obtained by soaking PEI-PAA@SiO2 in HAuCl4 solution and subsequent calcination. The Au@HPSNs show extremely high catalytic efficiency for 4-nitrophenol (4-NP) reduction with NaBH4, and exhibit the highest heterogeneous Au-based catalytic efficiency up to date for 4-NP reduction. The greatly enhanced performance of Au@HPSNs could be ascribed to ultra-fine Au nanoclusters and the small mass transfer hindrance with high specific surface area hollow porous silica.

Automated summary

In this study, Au nanoparticles were synthesized and encapsulated in hollow porous silica nanospheres (Au@HPSNs). The Au@HPSNs consisted of extremely small Au nanoclusters (-1.3 nm) enclosed in high specific surface area (-800 m2/g) HPSNs. The formation of PEI-PAA@SiO2 core-shell structures was achieved by using electrostatic attraction between poly(acrylic acid) (PAA) anions and protonated poly(ethylenimine) (PEI) in an ethanol-water system. The Au@HPSNs were obtained by soaking PEI-PAA@SiO2 in HAuCl4 solution and subsequent calcination. The Au@HPSNs exhibited highly efficient catalytic activity for 4-nitrophenol (4-NP) reduction with NaBH4, surpassing the current record for heterogeneous Au-based catalysts in 4-NP reduction. The enhanced performance of Au@HPSNs can be attributed to the ultra-fine Au nanoclusters and the small mass transfer hindrance with high specific surface area hollow porous silica.