Highly efficient Z scheme heterojunction of colloidal SnO2 quantum dots grafted g-C3N4

What is it about?

The strategic design of the heterojunction photocatalyst with an enhancement in the charge transfer rate of photogenerated charge carriers plays a key role in wastewater treatment to remove organic pollutants. In the current study, the heterojunction of g-C3N4/SnO2 quantum dots (g-CN/c-SQDs) with different ratios of SQDs was prepared via sonochemical route. The Z scheme for the photocatalyst of g-CN/c-SQDs in visible light exhibits an exceptional degradation performance of RhB dye (98.25 % in 40 min) with cyclic stability. The enhancement of photocatalytic degradation efficiency is ascribed to efficient charge transfer and redox reactions due to the design of the heterojunction between high surface areas of g-C3N4 and c-SQD, which is evident from the results from photoluminescence spectra and scavenger experiments. The free radical capture experiments reveal the electron transfer pathway and the generation of reactive oxygen species (ROS) generation, including superoxide (•O2–) and hydroxyl (•OH) radicals has been involved in the photocatalytic degradation process. This study provides an insight of the construction of the Z- scheme heterojunction with an appropriate amount of semiconductor for an enhancement of photodegradation efficiency in wastewater treatment.

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Why is it important?

Z-scheme g-C3N4/SnO2 quantum dots (QDs) photocatalyst to improve photocatalytic performance for environmental remediation and sustainable energy applications. It discusses the synthesis process, which involves creating g-C3N4 and SnO2-QDs and combining them in specific ratios to enhance their ability to degrade organic pollutants under solar irradiation. The research aims to address the limitations of single-component photocatalysts by achieving effective charge separation, increased carrier lifetime, and better utilization of solar energy. The X-ray diffraction (XRD) analysis shows the formation of a heterojunction between g-CN and SnO2 QDs, confirmed by characteristic diffraction peaks of both materials. The merging and slight shift of the peaks, along with decreased peak intensity as SnO2 QDs content increases, indicate good crystallinity and effective integration of SnO2 into the g-CN structure. The absence of impurity peaks and the small grain size of SnO2 QDs (2–2.5 nm) further validate the high purity and structural integrity of the hybrid nanostructure. The g-CN/c-SQDs-6 heterostructure, prepared via sonochemical synthesis, demonstrated significantly enhanced photocatalytic efficiency, achieving 98.25% degradation of RhB dye under visible light, due to reduced electron-hole recombination and the presence of reactive species •O2– and •OH.

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