Synergistic enhancement in carbon nitride quantum dots@NaBiO3 for solar-driven photocatalysis: A combined experimental and theoretical study

Abstract

The fast growth of industrialization and the increase in chemical use have made water pollution a serious issue that endangers both the environment and people. Pollutants in wastewater have serious environmental and health issues. This research examines the synergetic effect of a novel metal-free nanocomposite, carbon nitride quantum dots (CNQDs) anchored to NaBiO₃ photocatalyst. CNQDs@NaBiO₃ nanocomposites were successfully synthesized to harvest solar light and to remove contaminants like pesticides, pharmaceuticals, and dyes. CNQDs@NaBiO₃ was characterized utilizing available techniques, including scanning electron microscopy–Energy Dispersive X-ray, Fourier-transfer infrared spectroscopy, x-ray diffraction (XRD), UV–visible, and DRS spectroscopy. The removal efficiency was assessed for methylene blue, eosin yellowish, tetracycline, and trifluralin under visible light exposure and solar light. The resulting rate constant of degradation is remarkably efficient for all molecules, and its kinetics were second-order for all: trifluralin 0.1828 M min⁻¹, tetracycline 0.2249 M min⁻¹, methylene blue 0.1438 M min⁻¹, and eosin yellowish 0.1579 M min⁻¹. It is worth mentioning that CNQDs@NaBiO₃ works at a temperature range of 15–45°C and shows maximum degradation at 15°C. The trapping experiments were also conducted to determine the ROS involved in degradation and the mechanism. Experimental findings indicate that all active species, h⁺, e⁻, O₂^−•, and •OH, are involved in degradation. DFT simulation was performed to reveal details about the newly designed CNQDs@NaBiO₃ nanocomposite compared to NaBiO₃, and for this reason, optical and electronic properties were computed. Theoretical results showed that CNQDs have a synergetic effect on NaBiO₃, which provides extra bands, an extended band edge, and a broadened spectrum of light absorption that is more useful in solar light harvesting.