Synergistic effect of Fe doping and oxygen vacancy in AgIO3 for effectively degrading organic pollutants under natural sunlight

In this work, a series of hydrogenated Fe-doped AgIO3 (FAI-x) catalysts are synthesized for photodegrading diverse azo dyes and antibiotics. Under the irradiation of natural sunlight with a light intensity of ∼60 mW/cm2, the optimum FAI-10 exhibits a considerable rate constant for decomposing methyl orange (MO) of 0.067 min-1, about 7.4 times higher than that of AgIO3 (0.009 min-1), and 24.6% and 83.8% of MO can be decomposed over AgIO3 and FAI-10 after irradiation for 40 min. In the amplification photodegradation experiments with using 0.5 g catalyst and 400 mL MO dye solution (10 mg/L), FAI-10 possesses greatly higher photoreactivity to common semiconductors (ZnO, TiO2, In2O3 and Bi2MoO6), and the photodegradation rates over FAI-10 are 92%. Particularly, the FAI-10 shows superior stability, the activity of which remains unaltered after 8 continuous cycles. Foreign ions and water bodies have slight effect on the activity of FAI-10, but the MO degradation rates are decreased by adjusting pH values, especially when pH = 11 because of the strong electrostatic repulsion between MO and FAI-10. FAI-10 can also effectively decompose another azo dye (rhodamine B (RhB)) and diverse antibiotics (sulflsoxazole (SOX), chlortetracycline hydrochloride (CTC), tetracycline hydrochloride (TC) and ofloxacin (OFX)). The activity enhancement mechanism of FAI-10 has been systemically investigated and is ascribed to the promoted photo-absorption, charge separation and transfer efficiency, and affinity of organic pollutants, owing to the synergistic effect of Fe doping and oxygen vacancy (Ov). The photocatalytic mechanisms and process for decomposing MO are verified and proposed based on radical trapping experiments and liquid chromatography-mass spectrometry (LC-MS). This work opens an avenue for the fabrication of effective photocatalysts toward water purification.

Core-shell structured Z-scheme Ag2S/AgIO3 composites for photocatalytic organic pollutants degradation

Constructing direct Z-scheme system is a promising strategy to boost the photocatalytic performance for pollution waters restoration, but it is of great challenge because of the requirement of appropriately staggered energy band alignment and intimate interfacial interaction between semiconductors. Herein, a class of core-shell structured Ag₂S-AgIO₃ Z-scheme heterostructure photocatalysts are designed and developed. Ag₂S is generated by the in-situ ion exchange reaction and anchored on the surface of AgIO₃, so the intimate interface between AgIO₃ and Ag₂S is realized. Integration of AgIO₃ and Ag₂S extends the ultraviolet absorption of AgIO₃ to Vis-NIR region, and also promote the charge separation and migration efficiency, contributing to the enhanced photocatalysis activity for composite catalysts. The optimal Ag₂S-AgIO₄-4 catalyst exhibits a MO photo-degradation rate constant of 0.298 h^-1, which reaches 5.77 and 11.4-folds higher than that of AgIO₃ (0.044 h^-1) and Ag₂S (0.024 h^-1). The as-obtained composite catalyst exhibits universally photocatalytic activity in disintegrating diverse industrial pollutants and pharmaceuticals. Particularly, driven by natural sunlight, the Ag₂S-AgIO₄-4 can effectively decompose MO. A plausible Z-scheme photocatalytic mechanism and reaction pathways of MO degradation over composite catalyst are systemically investigated and proposed.