Ag2S-doped core-shell nanostructures of Fe3O4@Ag3PO4 ultrathin film: Major role of hole in rapid degradation of pollutants under visible light irradiation

Abstract

Ag2S-doped core-shell nanostructures of Fe3O4@Ag3PO4 ultrathin film were synthesized via solvothermal deposition of Ag3PO4 on Fe3O4 nanoparticles, followed by an in-situ anion-exchange reaction between Ag3PO4 and Na2S at room temperature. The optimal photocatalyst, b-Ag2S/Fe3O4@Ag3PO4-100, exhibited highly efficient visible-light photocatalytic activity and anti-photocorrosion compared to pure Ag3PO4. Organic micropollutants (OMPs), including neonicotinoid insecticides (e.g., imidacloprid and thiacloprid) and antibiotics (e.g., difloxacin hydrochloride and sulfadizine) were efficiently and rapidly photodegraded by the b-Ag2S/Fe3O4@Ag3PO4-100 under visible light irradiation. More importantly, environmental factors including pH, natural organic matter and inorganic salts (e.g., NaNO3, NaCl and CaCl2) showed negligible effects on the photocatalytic activity of the novel catalyst, which was further validated by environmental water (e.g., lake, river and underground water) treatment. After 4 cycles, the b-Ag2S/Fe3O4@Ag3PO4-100 could still degrade > 83.9% imidacloprid, showing less dissolved silver leaching compared to Fe3O4@Ag3PO4-100 and pure Ag3PO4, which suggested its superior stability. The enhanced photocatalytic activity and stability were primarily related to an effective separation of photogenerated charge carriers due to doping Ag2S crystals into ultrathin Ag3PO4 film. Reactive species in particular photogenerated hole primarily contributed to the activity of novel photocatalyst toward OMPs. This work exhibited the applicability and superiority of Ag2S-doped core-shell nanostructures of Fe3O4@Ag3PO4 ultrathin film for environmental remediation of OMPs.