Synthesis, characterization, enhanced sunlight photocatalytic properties, and stability of Ag/Ag3PO4 nanostructure-sensitized BiPO4

Abstract

This novel Ag/Ag₃PO₄ nanostructure-sensitized BiPO₄ (Ag/Ag₃PO₄/BiPO₄) photocatalyst was synthesized using hydrothermal and impregnation processes. Powder X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, Raman spectroscopy, IR spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy were used to characterize the as-prepared products. The optical properties and morphology of BiPO₄ exhibited drastic changes and were dependent on the AgNO₃ concentration. Regarding methylene blue (MB), rhodamine B, and methyl orange degradation under solar irradiation (95% degradation within 5 min), 15% Ag/Ag₃PO₄/BiPO₄ exhibited considerably higher photocatalytic activity than BiPO₄ and P25. After five cycles, Ag/Ag₃PO₄/BiPO₄ exhibited no apparent loss of activity, confirming its stability despite recycling. The practicality of this Ag/Ag₃PO₄/BiPO₄ was validated according to its ability to degrade MB in seawater, pond water, and industrial wastewater samples, which also demonstrated the advantages of its high photocatalytic activity. Moreover, 15% Ag/Ag₃PO₄/BiPO₄ also showed sunlight-induced photocatalytic disinfection activity toward E. coli cells. The enhanced photocatalytic activity and improved stability of Ag/Ag₃PO₄/BiPO₄ could be attributed to the strong visible light absorption by Ag/Ag₃PO₄ nanostructures, a low electron–hole recombination rate, and the highly efficient separation of photogenerated electron–hole pairs throughout Ag₃PO₄/BiPO₄ heterostructures. Moreover, holes were the main reactive species.