Synthesis of Ag3PO4/SnO2 composite photocatalyst for improvements in photocatalytic activity under visible light

Ag3PO4/SnO2 composites with various molar ratios of SnO2 were synthesized by a simple in situ precipitation method. All the obtained samples were structurally, optically, and morphologically characterized by various techniques, such as X-ray diffraction, Rietveld refinement, micro-Raman, Fourier transform infrared, UV–Vis diffuse reflectance, and photoluminescence spectroscopies. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were also utilized, wherein the Ag3PO4 microparticles were in contact with the SnO2 nanoparticles and microrods. The interaction between the two phases was confirmed based on the improvement in the photocatalytic performance for the degradation of an aqueous solution of Rhodamine B dye when exposed to visible light irradiation (>400 nm). The photocatalytic performance increased significantly in the composites with 5%–15% SnO2, followed by a slight decrease in the composite with 20% SnO2. The rate of reaction of the composite with 15% SnO2 was approximately 3.0 times higher than that of pure Ag3PO4. From the experimental results, a possible photocatalytic mechanism for the pure Ag3PO4 and the composite with 15% SnO2 was proposed, showing that the superoxide radicals contributed significantly to the improvement of the photocatalytic activity of the composite. In addition, the photocatalytic mechanism observed in the composites was associated with the formation of a possible p-n junction between Ag3PO4 and SnO2.