Highly efficient Z scheme heterojunction of colloidal SnO2 quantum dots grafted g-C3N4 for the degradation of rhodamine B under visible light

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.