Highly effective and stable Ag3PO4–WO3/MWCNTs photocatalysts for simultaneous Cr(VI) reduction and orange II degradation under visible light irradiation

Abstract A series of high-performance photocatalysts of Ag 3 PO 4 –WO 3 /multi-walled carbon nanotubes (MWCNTs) were fabricated through a deposition–precipitation method. Their structures and physical properties were characterized by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), specific surface analyzer, X-ray diffraction (XRD), UV–vis absorption spectra, photoluminescence spectra (PL) and X-ray photo-electron spectroscopy (XPS). SEM, EDS and TEM analyses verified that Ag 3 PO 4 –WO 3 /MWCNTs composites have been successfully prepared. PL analysis illustrated that Ag 3 PO 4 –WO 3 /MWCNTs have the lower emission peak intensities, compared with Ag 3 PO 4 and WO 3 . By using simultaneous decontaminations of Cr(VI) and orange II as model reactions, the photocatalytic efficiencies of Ag 3 PO 4 , WO 3 and Ag 3 PO 4 –WO 3 /MWCNTs were evaluated. The reaction results showed that Ag 3 PO 4 –WO 3 /MWCNTs have strong photocatalytic activities. The effect of Ag 3 PO 4 :WO 3 ratio on the photocatalytic activity was systemically studied. The catalyst AWM 7/3 was found to exhibit the highest photocatalytic activity and excellent chemical stability in repeated and long-term applications. The improvement of photocatalytic activity and stability was mainly attributed to the highly effective separation of photo-generated electron–hole pairs and special transfer pathway of electrons and holes in Ag 3 PO 4 –WO 3 /MWCNTs composites. Therefore, the prepared Ag 3 PO 4 –WO 3 /MWCNTs could act as a high-performance catalyst for the simultaneous decontaminations of Cr(VI) and orange II, and also suggested the promising applications.