Abstract:

The composites of Ag₃PO₄/BiVO₄/Sr₂MgSi₂O₇: （Eu²⁺, Dy³⁺） （ABS） with all-weather photocatalytic activity were prepared by constructing heterojunction using Sr₂MgSi₂O₇: （Eu²⁺, Dy³⁺）, Ag₃PO₄ and BiVO₄ as raw materials. These ABS composites were systematically characterized by SEM, XPS, UV-vis DRS, PL and EIS. Methylene blue （MB） dye solution was used as the target pollutant. The all-weather photocatalytic activity and stability of ABS composites were evaluated, and a dual Z-scheme charge transfer mechanism of photocatalysis in light and dark environments was proposed. The results showed that the degradation percentage of MB dye solution by ABS composite with the mass ratio of 1∶1∶40 reached 98.8% after 15 min of simulated sunlight irradiation and 15 min of continual reaction in dark environment. The degradation percentage of MB dye solution still reached 98.5% after 5 cycles, indicative of good all-weather photocatalytic activity and stability. Benefiting from the coupling of Ag₃PO₄, BiVO₄ and Sr₂MgSi₂O₇: （Eu²⁺, Dy³⁺）, the construction of dual Z-scheme heterojunction effectively promoted the separation of photoelectron-hole and effectively retained the high-oxidation-potential valence band of Ag₃PO₄ and BiVO₄. Under light conditions, Sr₂MgSi₂O₇: （Eu²⁺, Dy³⁺） accumulated energy by filling the defect energy. The energy released in the dark environment stimulated the charge separation of Ag₃PO₄ and BiVO₄, and the high-oxidation-activity holes in the valence band could oxidize H₂O to hydroxyl radicals （·OH）. Then efficient degradation of organic dye MB was achieved under the actions of ·OH and holes.

Key words: Ag₃PO₄, BiVO₄, Sr₂MgSi₂O₇:（Eu²⁺, Dy³⁺）, all-weather photocatalysis, double Z-scheme heterojunction, methylene blue