Engineering a carbon quantum dot-bridged CuInS₂/MnFe-BTC/g-C₃N₄ Z-scheme photocatalyst for efficient removal of organic pollutants from water

Abstract

Developing efficient, eco-friendly photocatalysts is essential to address water pollution by persistent organic contaminants like antibiotics and synthetic dyes. This study introduces a novel Z-scheme photocatalyst, CuInS2/ MnFe-BTC/g-C3N4 (“CMG”) integrated with carbon quantum dots (CQD-CMG), synthesized through a green, microwave-assisted hydrothermal method, for visible-light-driven degradation of tetracycline (TC) and Reactive Yellow 145 (RY-145) dye. The resulting photocatalyst exhibited a high surface area (1031.5 m2/g), nanoparticle size (20–40 nm), broad visible-light absorption, and excellent charge separation efficiency (0.342 µA/cm2). The integration of carbon quantum dots significantly enhanced charge transfer and suppressed electron–hole recombination, as evidenced by electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) measurements. Under visible-light irradiation, CQD-15 %CMG achieved outstanding degradation efficiencies of 98.2 % for TC and 98.6 % for RY-145. Operational factors such as pH, pollutant concentration, catalyst dosage, coexisting anions, humic substances, and material reusability were thoroughly evaluated. Radical scavenging experiments and electron spin resonance (ESR) analysis identified •OH and •O2– as the dominant reactive species. Band structure analysis via UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) and Mott–Schottky analysis confirmed that the photocatalytic mechanism followed an efficient Z-scheme charge transfer pathway. This work highlights the potential of CQD-CMG as a high-performance, sustainable photocatalyst for the remediation of contaminated water, offering a promising solution for advanced water purification technologies. Show more