A PW₁₂/Ag functionalized mesoporous silica-coated magnetic Fe₃O₄ core–shell composite as an efficient and recyclable photocatalyst

Abstract

The novel composite, Fe₃O₄@SiO₂@mSiO₂-PW₁₂/Ag, was successfully prepared by in situ loading Ag nanoparticles (Ag NPs) on the surface of grafted phosphotungstate (denoted as PW₁₂) Fe₃O₄@SiO₂@mSiO₂via a photoreduction deposition method. PW₁₂ not only acts as a reducing agent and stabilizer for Ag NPs but also as a bridge to link Ag NPs and the SiO₂ shell in the loading process. Its activity toward the photodegradation of methyl orange (MO) and photoreduction of Cr₂O₇^2- anions was evaluated. Experimental results showed that Fe₃O₄@SiO₂@mSiO₂-PW₁₂/Ag with 5.3 wt% Ag loading and 18.65 wt% of PW₁₂ exhibits the highest photocatalytic efficacy, and complete degradation of MO and 91.2% photoreduction of Cr(vi) were realized under simulated sunlight for 75 min, respectively. The enhanced catalytic activities of the composite are due to its high specific surface area, the synergistic effect among the components and the formation of a heterojunction of PW₁₂/Ag. The possible enhanced photocatalytic mechanism is proposed. The catalyst is durable and can be easily recovered using a magnet for recycling without a significant loss of catalytic activity.