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 Ag3PO4–WO3/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 Ag3PO4–WO3/MWCNTs composites have been successfully prepared. PL analysis illustrated that Ag3PO4–WO3/MWCNTs have the lower emission peak intensities, compared with Ag3PO4 and WO3. By using simultaneous decontaminations of Cr(VI) and orange II as model reactions, the photocatalytic efficiencies of Ag3PO4, WO3 and Ag3PO4–WO3/MWCNTs were evaluated. The reaction results showed that Ag3PO4–WO3/MWCNTs have strong photocatalytic activities. The effect of Ag3PO4:WO3 ratio on the photocatalytic activity was systemically studied. The catalyst AWM7/3 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 Ag3PO4–WO3/MWCNTs composites. Therefore, the prepared Ag3PO4–WO3/MWCNTs could act as a high-performance catalyst for the simultaneous decontaminations of Cr(VI) and orange II, and also suggested the promising applications.