Ag3PO4 anchored SnWO4 Z-scheme heterojunction for reactive blue 21 degradation: Performance analysis and mechanism insights

Abstract

The Ag3PO4–SnWO4 heterostructured nanocomposites have been prepared by the chemical precipitation process. The prepared nanocomposites were examined through XRD, TEM, UV–visible NIR, PL, BET, Mott Schottky, EIS, and ESR measurements. The diffraction peaks of Ag3PO4–SnWO4 nanocomposite showed the peaks of SnWO4 nanoparticles that are orthorhombic in the Ag3PO4 tetragonal structure, which suggested that they are present in the mixed phase of the composite. Photoluminescence spectra displayed efficiency in charge separation of e−-h+ pairs in Ag3PO4–SnWO4-1 nanocomposite. The Ag3PO4–SnWO4 nanocomposites have been examined for degrading the aqueous solution of reactive blue (RB 21) under natural sunlight irradiation. The superior photoactivity of Ag3PO4–SnWO4-1 could be ascribed to the existence of a heterostructure between Ag3PO4 and SnWO4 nanoparticles that improved the light absorption ability of the heterostructure. Also, a low rate of recombination of electron and hole pairs between Ag3PO4 and SnWO4 nanoparticles was observed. The Mott–Schottky plot revealed both Ag3PO4 and SnWO4 as n type semiconductor with flat-band potential values as 0.34 and −0.54 eV respectively. The photocatalytic rate reached the fastest on the incorporation of 100 mg SnWO4 compared to pristine Ag3PO4 and SnWO4 particles with 91.4% degradation efficiency and a rate constant of 0.257 min−1. The photogenerated O2∙−, h+ and ∙OH radicals indicated by the radical trapping experiment were mainly liable for the RB 21 degradation.

Keywords

• Ag3PO4–SnWO4
• Heterostructure
• Nanocomposite
• photoluminescence
• Photodegradation
• Reactive blue 21