Silver nanoparticles modified reduced graphene oxide wrapped Ag3PO4/TiO2 visible-light-active photocatalysts with superior performance

Abstract

Silver nanoparticles (Ag NPs) modified reduced graphene oxide wrapped Ag₃PO₄/TiO₂ (Ag₃PO₄/TiO₂/Ag-rGO, Ag-ATG) photocatalysts have been developed through a rational design that combines the optimization of charge generation, separation and transfer in the composites, which helps to increase the photocatalytic performance. The Ag-ATG composites possess novel microstructure, in which TiO₂ mesoporous spheres of hundreds of nanometers in size are decorated with dense nano-sized Ag₃PO₄ to form pinecone-liked Ag₃PO₄/TiO₂ particles, which were further wrapped by rGO sheets that are selectively decorated with Ag NPs. The Ag-ATG composites exhibit improved photocatalytic performance toward degradation of methylene blue (MB) and methyl orange (MO) under visible light compared to bare Ag₃PO₄ and Ag₃PO₄/TiO₂/rGO (ATG). The underlying mechanism has been studied based on the results of reactive oxygen species capture experiment, photoluminescence (PL) spectra, and photocurrent measurements under visible light and monochromatic lights. The improved photocatalytic performance is mainly ascribed to the efficient spatial separation of photo-induced electrons and holes in Ag-ATG, i.e., the electrons in Ag₃PO₄ transfer to Ag-rGO, meanwhile the holes in Ag₃PO₄ transfer to TiO₂. Ag NPs play an important role in the hybrid structure owing to the synergistic effect of Ag NPs and rGO, which not only enhance the light harvest but also increase the capacity of electron accepting from Ag₃PO₄. Meanwhile, active photo-induced electrons at the plasmonic Ag NPs can facilitate the formation of O₂˙⁻ radicals for photocatalysis. As a result, both the stability and photocatalytic active of Ag-ATG are significantly improved.