Enhanced visible-light-driven photoelectrochemical and photocatalytic performance of Au-SnO2 quantum dot-anchored g-C3N4 nanosheets

Abstract

A novel g-C3N4/Au-SnO2 quantum dot (g-CN/Au-SQD) ternary nanocomposite was fabricated via a three-step approach for the degradation of the organic pollutant rhodamine B (RhB), and photoelectrochemical (PEC) water splitting upon visible light illumination. Au-SQDs were prepared via a one-pot chemical reduction method, and g-CN was synthesized via the thermal polymerization of urea at 550 °C. The g-CN/Au-SQD ternary nanocomposite was prepared via sonication, stirring, and finally annealing. This approach was effective for the mixing and dispersion of Au-SQDs over the entire surface of the two-dimensional (2D) g-CN nanosheets. Morphological studies revealed that the Au-SQDs were well-distributed over the nanolayers of the g-CN. The light-capturing ability was improved and optimized with the loading of different amounts of Au-SQDs. The bandgap was tuned from 2.85 eV (g-CN) to 2.58 eV (g-CN/Au-SQD). Photoluminescence analysis revealed the inhibited nature of recombination of electrons and holes in the ternary nanocomposites. Optimization yielded CNAS-20, which exhibited the best photocatalytic performance within 40 min for the degradation of the pollutant RhB. Furthermore, the CNAS-20 photoelectrode showed lower charge-transfer resistance than the other prepared samples, which was favorable for PEC water splitting. The CNAS-20 photoelectrode exhibited a significant photocurrent, which was ~3.83 times greater than that of pure g-CN. Thus, this unique design incorporates a 2D g-CN and plasmonic Au metal nanoparticles for the generation of photoexcited electrons, and SQDs receive these photogenerated electrons to increase the leave-taking of electron and holes to enhance the photocatalytic and PEC activities.