Heterointerface engineered and highly dual-functional N-doped carbon dot /N-rich g-C₃N₄ hybrid photocatalysts

Coupled oxidation and reduction of 4-nitrophenol (4NP) and Cr(VI) offer unique advantages for wastewater treatment. In this study, nitrogen-doped carbon dots (NCDs) were decorated on the surface of nitrogen-rich g-C₃N₄ (NCN) for simultaneous removal of 4NP and Cr (VI). The structural, optical, and electronic properties of the prepared catalysts were also investigated. The optimized 2.0% NCD/NCN catalyst exhibited excellent photocatalytic activity for the simultaneous removal of Cr(VI) (97%) and 4NP (95%) within 60 min under visible light by photogenerated electrons and holes, respectively. This superior photoactivity is attributed to the outstanding visible-light absorption, electron transferability, up-conversion photoluminescent properties and photosensitizing effect of NCDs. NCDs on the NCN surface improve the photocatalytic efficiency by minimizing undesired electron-hole recombination with a consequent increase in the lifetime of the heterostructure, as confirmed by photoluminescence, time resolved photoluminescence Spectroscopy, and Electrochemical impedance spectroscopy. Additionally, the synergistic photocatalytic effect of the coexisting systems is due to the increasing electron traps of Cr(VI), and hole entraps of 4NP. To confirm the presence and contribution of the active species, free-radical quenching experiments, spectral analysis, and electron spin resonance measurements were performed. This unique OD/2D hybrid catalyst has enormous potential for effectively removing organic and inorganic pollutants from polluted industrial water without adding additional chemical reagents.