Boosting the photodegradation of rhodamine B with the CuWO4/g-C3N4 heterojunction by introducing biomass derived N-CQDs as an electron mediator: mechanism and DFT calculations

A Z-scheme heterojunction CuWO4/N-CQD/g-C3N4 (CWO/N-CQD/CN) was constructed using Euphorbia neriifolia leaf derived N-CQDs (nitrogen-doped carbon quantum dots) as an electron mediator. Among the nanocomposites prepared with different ratios of CWO and N-CQD/CN, the 0.2-CWO/N-CQD/CN nanocomposite exhibits excellent photocatalytic degradation efficiency for rhodamine B (RhB) up to 97.8% under visible light irradiation as compared to the binary CWO/CN and N-CQD/CN composites. The reduced photoluminescence intensity and higher lifetime reveal the formation of a heterojunction between the nanoparticles, thereby lowering the recombination of electron-hole pairs. Reactive oxygen species scavenging assays have established that hydroxyl radicals ((OH)-O-center dot), holes (h(+)) and singlet oxygen (O-1(2)) are the primary reactive species in RhB dye degradation. A Z-scheme photocatalytic mechanism was suggested based on the DFT calculations and band structure of CWO/N-CQD/CN. The effect of various parameters like pH, catalyst amount, H2O2 concentration, and dye content was also examined in RhB degradation. Moreover, the Z-scheme photocatalyst possesses good recyclability up to the fourth cycle. Using the LC-MS approach, the degradation of RhB into smaller organic moieties was also observed. Hence, this study provides a unique perspective on developing an effective Z-scheme photocatalyst that has practical utility in environmental remediation.

Automated summary

In this study, a Z-scheme heterojunction CuWO4/N-CQD/g-C3N4 photocatalyst was constructed using Euphorbia neriifolia leaf derived nitrogen-doped carbon quantum dots (N-CQDs) as an electron mediator. The 0.2-CWO/N-CQD/CN nanocomposite exhibited excellent photocatalytic degradation efficiency for rhodamine B (RhB) under visible light irradiation. A Z-scheme photocatalytic mechanism was suggested based on DFT calculations and band structure analysis. The study also investigated the effects of various parameters on RhB degradation and demonstrated the recyclability of the Z-scheme photocatalyst.