Facile synthesis of highly efficient Co@ZnSQDs/g-C3N4/MWCNT nanocomposites and their photocatalytic potential for the degradation of RhB dye: Efficiency, degradation kinetics, and mechanism pathway

Abstract Modification of graphitic carbon nitride (g-C3N4) with Co-doped zinc sulfide quantum dots (Co@ZnSQDs) and multiwalled carbon nanotubes (MWCNT) significantly improved the photodegradation performance of rhodamine B (RhB) in aqueous suspension under visible light. Herein, a strong heterojunction and highly efficient novel ternary nanocomposites Co@ZnSQDs/g-C3N4/MWCNT (Co-ZGM) with different mass ratios were successfully prepared by thermal impregnation technique. The synthesized materials were characterized by using analytical research instruments such as XRD, FTIR, DRS, XPS, SEM, FE-SEM, HR-TEM, EDX, BET surface area analysis, photoluminescence, and UV–vis spectroscopy. DRS result reveals that light absorption spectra are extended to the visible region. XPS study reveals that Co ion is successfully doped into ZnSQDs nanocatalyst. The EDX analysis shows that all relevant elements are present in our synthesized composite materials. The photodegradation results clearly indicate that 7 wt% Co@ZnSQDs/g-C3N4/MWCNT (7Co-ZGM) nanocomposite exhibits enhanced photocatalytic performance, and about 96% degradation of RhB dye was observed within 75 min. The remarkable improved photodegradation performance of 7Co-ZGM nanocomposite could be related to the high separation of electron-hole pairs (due to formation of heterojunction), proficient absorption of visible light, enlarged specific surface area, and strong redox ability of photoinduced charge carriers. Additionally, photo mineralization of paracetamol was also assessed by examining the reduction in total organic carbon (TOC) contents as a function of time over the most active 7Co-ZGM nanocomposite under visible light illumination. The quenching experiments were performed to know about the core reactive species involved in the photocatalytic degradation path. This study offers a simple, structurally controllable, effective, and significant route for the synthesis of visible light (low energy) active heterogeneous catalysts and highlights the importance of its potential for the degradation of environmental pollutants. A possible photocatalytic mechanism using different electron-hole pair acceptors has been proposed for improved photodegradation performance.