Magnetic core–shell carbon microspheres (CMSs)@ZnFe2O4/Ag3PO4 composite with enhanced photocatalytic activity and stability under visible light irradiation

• Magnetic core–shell carbon microspheres (CMSs)@ZnFe2O4/Ag3PO4 photocatalyst was first fabricated.
• Degradation efficiency and apparent rate constant of 2,4-DCP over the composite were enhanced.
• Synergistic effect of CMSs, ZnFe2O4, Ag3PO4 contributes to the improved photocatalytic performance of the composite.
• Possible pathway of the photoinduced carrier transfer and formation of the free radicals in the system were discussed.

Novel magnetic core–shell visible light responsive carbon microspheres (CMSs)@ZnFe2O4/Ag3PO4 composite photocatalyst with different mass ratios have been successfully synthesized through the solvothermal and in situ precipitation methods for the first time. The characteristics of the as-prepared materials were systematically determined by the XRD, XPS, SEM, FESEM-EDS, UV–vis DRS, VSM, and PL etc.; the results indicated that all of the composites showed good crystallinity and strong absorbance both in the UV and visible light regions. Moreover, a heterojunction structure was formed between the ZnFe2O4 and Ag3PO4. The photocatalytic performance of the composite was evaluated for 2,4-dichlorophenol (2,4-DCP) degradation, and enhanced photocatalytic activity and stability were achieved. When the mass ratio of CMSs, ZnFe2O4, and Ag3PO4 in the composite was 2:1:3, the apparent photodegradation rate constant of 2,4-DCP was 0.0184 min−1, which was 7.36 times that of ZnFe2O4, 2.45 times that of Ag3PO4, and 4 times that of CMSs@ZnFe2O4 (mass ratio = 2:1). And after four times recycling, the photodegradation efficiency of 2,4-DCP over the CMSs@ZnFe2O4/Ag3PO4 (mass ratio = 2:1:3) can even reach approximately 89%. The investigation of the photocatalytic mechanism suggested that both the effective separation of the photoinduced electron–hole pairs and the active free radicals formed in the special core-shell interface contributed to the superior photocatalytic performance of the composite.

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