Green Synthesis of Ag/TiO2 Composites Coated Porous Vanadophosphates with Enhanced Visible-Light Photo-degradation and Catalytic Reduction Performance for Removing Organic Dyes

ABSTRACT: As the environmental pollution and energy shortages become the global concern, the construction of highly efficient catalysts using facile and green methods remains a long-term goal. In the present study, we proposed a facile catalysts preparation method in which Ag/TiO2 composites were coated on the surface of the porous pure inorganic crystalline vanadium phosphates (VPO) by one-step strategy. More importantly, in situ reduction of Ag nanoparticles were achieved at room temperature without severe conditions or hydrogen atmosphere in which the porous VPO was employed as the reductant. The prepared Ag/VPO@TiO2 composites act as a class of efficient bifunctional catalysts for visible light photodegradation of MB molecules and catalytic reduction of p-nitrophenol (4-NP). Among these samples, 6.82%Ag/VPO@TiO2 composite exhibited superior photocatalytic activity in the degradation of MB and an ultrafast reduction rate for 4-NP about 0.1 mM/40 s. The photocatalytic mechanistic studies revealed that the encapsulated VPO with a narrow band gap not only efficiently enhances photosensitivity of the TiO2, but also largely facilitates the photogenerated charge separation. The subsequent deposition of Ag NPs is able to further promote electron transfer ability, which leads to the higher photocatalytic activity. Moreover, the contact of Ag NPs with the surface of semiconductor TiO2 can result in an electron-enhanced area in their interface, which could effectively facilitate the uptake of electrons by the 4-NP molecules and then improve the reduction activity.