BiPO4/Ag3PO4 p-n Heterojunction with Enhanced Photocatalytic Activity under Simulated Sunlight Irradiation

BiPO4, Ag3PO4 and BiPO4/Ag3PO4 heterostructure photocatalysts were synthesized by one-step hydro-thermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) techniques were used to characterize morphology, crystal structure, and absorption spectrum. The SEM results showed that the BiPO4/Ag3PO4 sample was in blocky structure and BiPO4 distributed on the surface of Ag3PO4. The XRD of BiPO4/Ag3PO4 sample displayed monoclinic and cubic crystal structure. The UV-Vis DRS spectra results indicated that the BiPO4/Ag3PO4 sample displayed obviously red shifts compared to BiPO4 and the light absorption range broaden to 571 nm. Moreover, the photocatalytic activity was evaluated by photodegradation of methyl orange (MO) and gatifloxacin solution under simulated sunlight irradiation. BiPO4/Ag3PO4 exhibits higher degradation and mineralized activities and the better stability on degradation of methyl orange and gatifloxacin than the single BiPO4 and Ag3PO4. Moreover, the test of active radical showed that the h(+) was the main active radical in the degradation process, center dot O-2(-) was weaker. The enhanced photocatalytic activity and stability of BiPO4/Ag3PO4 was mainly attributes to the formation of p-n heterojunction interface in BiPO4/Ag3PO4 which facilitated the transfer and separation of photogenerated electron-hole pairs confirmed by the results of transient photocurrent response and electrochemical impedance spectroscopy measurement. Based on the above results, the photocatalytic mechanism for organics degradation over BiPO4/Ag3PO4 was proposed.