Engineering heterogeneous Z-scheme photocatalysts Fe-BTC/CuInS2/BiVO4 integrated with carbon quantum dots to enhance the efficiency of Cr(VI) reduction and RR-195 degradation under visible light

Abstract

In this study, Fe-BTC/CuInS₂/BiVO₄ composites (with Fe-BTC content ranging from 10 to 30 wt%) were synthesized followed by the incorporation of carbon quantum dots (CQDs) to form FCB-CQD photocatalysts. The resulting materials exhibit several key advantages, including high surface area, large pore volume, small particle size, efficient visible light absorption, and improved charge transport properties. The integration of CQDs significantly enhanced charge separation and reduced electron–hole recombination. A Z-scheme charge transfer mechanism was proposed and validated, enabling the FCB-CQD photocatalysts to achieve highly efficient photocatalytic reduction of Cr(VI) to Cr(III) and degradation of Reactive Red 195 (RR-195) under visible light. The 20%FCB-CQD sample achieved removal efficiencies exceeding 98 % for both pollutants. Key operational parameters, such as catalyst dosage, pollutant concentration, pH, reactive species involvement, and photocatalyst stability, were systematically investigated. Electrochemical and optical characterizations were used to construct the band structure and elucidate the electron transfer pathway. Scavenger experiments confirmed the dominant active species involved in each process, providing insight into the underlying photocatalytic mechanisms. These findings demonstrate the promising potential of FCB-CQD as an efficient and reusable photocatalyst for environmental remediation applications.