Enhanced photocatalytic degradation of organic dyes by carbon quantum dots-ZnFe2O4 composites

To safely cope with the hazardous methylene blue (MB) and rhodamine (RhB) dyes in wastewater, ZnFe2O4 has shown promise as attractive photocatalytic degradation material. Therefore, we synthesized CQDs-decorated ZnFe2O4 microspheres and successfully degraded MB and RhB dyes under UV light. The CQDs/ZnFe2O4 composites exhibited superior performance as compared to pure ZnFe2O4, achieving nearly 100% degradation of MB in 60 min and 95% degradation of RhB in 80 min. Additionally, the CQDs/ZnFe2O4 material was found stable after four consecutive cycles during the photocatalytic activity. Density functional theory calculations revealed that CQDs generated new gap states near the Fermi level, enhancing the charge separation and conductivity of the composites. The photocatalytic mechanism involved the generation of holes, .OH and .O2 radicals as the active species. These results demonstrate that CQDs/ZnFe2O4 composites can be promising candidates in wastewater treatment along with other wide range of applications.