Enhancing the photocatalytic efficiency of g-C3N4 by sonochemical dispersion of CdSe quantum dots for degradation of industrial organic pollutants under commercial light source

The fabrication of heterojunctions is a progressing approach to enhance the charge separation, transportation and visible light absorbability towards successful photocatalytic processes. In this research work, CdSe/g-C3N4 nanocomposites were tailored through coupling CdSe quantum dots as oxidative photocatalyst (EVB = +1.49 eV) with g-C3N4 as reductive photocatalyst (ECB = − 1.6 eV) for photocatalytic degradation of three different characteristics pollutants models; rhodamine B dye, amaranth dye and tetracycline. The physicochemical characteristics of the fabricated materials were analyzed by XRD [X-Ray diffraction], nitrogen adsorption isotherms, HRTEM [transmission electron microscope ‘high resolution’], SAED [selected area electron− diffraction], mapping, EDX [Energy dispersive X-ray spectroscopy], XPS [X-ray photoelectron spectroscopy], DRS [Diffuse-reflectance spectroscopy] and PL [photoluminescence]. XRD, HRTEM and SAED analysis revealed the co-existence of the two pristine materials confirming the successful construction of CdSe/g-C3N4 heterojunction. However, N2-adsorption isotherms implied the remarkable reduction in g-C3N4 surface area in the heterojunction due to dispersion of CdSe quantum dots on different active sites of g-C3N4 nanosheets. Incorporation of CdSe on g-C3N4 sheets shifted the absorbability towards visible region with a strong reduction in the charge carrier's recombination rate as confirmed from DRS and PL analysis. The photocatalytic performance of the as-synthesized heterojunctions was enhanced with introducing various proportions of CdSe quantum dots and reach an optimal value for the nanocomposite containing 5 wt % CdSe. The pseudo first order reaction rates for photocatalytic destruction of rhodamine B dye and tetracycline on the surface of CNCdSe5 was 2.2 and 5.9 folds higher than that over g-C3N4 surface, respectively. The transportation mechanism was illustrated by scavenger experiments and PL measurements of terephthalic acid, it was suggested to be S-Scheme mechanism. The results of this novel research revealed that the fabricated photocatalysts have robust redox performance in destroying various models of organic pollutants that dispersed in the wastewater. [Display omitted] •S-scheme CdSe/g-C3N4 heterojunctions engineered sonochemically.•CdSe quantum dots shift the absorbability of g-C3N4 to visible region.•Auspicious electron-hole separation and transportation rate are recorded.•The mechanism of charge transportation