Hollow mesoporous SiO2 sphere nanoarchitectures with encapsulated silver nanoparticles for catalytic reduction of 4-nitrophenol

Abstract

Ideally, a superior catalyst should possess high speed, selectivity and stability. However, it is difficult to holistically achieve high speed, selectivity and stability catalysis with modest configured catalyst structures. This work reports a new pre-shell/post-core approach combined with a laser ablation treatment strategy to fabricate a sophisticated catalyst architecture configured with a hollow mesoporous SiO₂ (hm-SiO₂) sphere shell and multiple encapsulated Ag nanoparticle (NP) yolks (Ag@hm-SiO₂). Each Ag@hm-SiO₂ nanosphere encapsulates 5–10 Ag NP yolks with an average size of 20 nm, in which the content of silver is about 3.6 wt% based on the inductively coupled plasma measurement. To further enhance the catalytic activity, a laser ablation treatment strategy is innovatively utilized to reduce the sizes of the encapsulated Ag NP yolks and increase their numbers. The catalytic reduction of 4-nitrophenol (4-NP) is used to evaluate the catalytic performance of the fabricated Ag@hm-SiO₂ catalyst architecture before and after laser ablation treatment. The laser ablation treated Ag@hm-SiO₂ nanospheres demonstrate a three-fold increased catalytic activity towards 4-NP reduction with excellent stability. Such superior catalytic performance could be attributed to the unique structural features of the Ag@hm-SiO₂ architecture, in which the mesopore shell provides not only readily accessible pathways for fast transport of reactants to the encapsulated Ag NPs but also an effective protective shield for the encapsulated Ag NPs.