Cu3P/Zn0.8Cd0.2S/g-C3N4 ternary nanocomposite for efficient visible-light-driven degradation of methylene blue through a dual Z-scheme photocatalytic configuration

This research intends to improve the photocatalytic efficiency of graphitic carbon nitride (g-C₃N₄) for visible-light–driven pollutant degradation by constructing a novel Cu₃P/Zn_0.8Cd_0.2S/g-C₃N₄ ternary nanocomposite. The synthesis of Cu₃P/Zn_0.8Cd_0.2S/g-C₃N₄ is conducted by a facile hydrothermal procedure. The structural characteristics, morphology, and photocatalytic properties of the composite were evaluated using XRD, FTIR, XPS, BET, FE-SEM, EDS, TEM, UV–Vis DRS, PL, EIS, photocurrent response, Mott-Schottky, and UV–Vis spectroscopy. The photocatalytic degradation of the aqueous solution of methylene blue was performed for 3 h under the irradiation of an LED lamp (100 W, 400–700 nm). The 5%-Cu₃P/Zn_0.8Cd_0.2S/g-C₃N₄ composite exhibited the highest photocatalytic efficiency, achieving a 95.64% degradation of MB within 180 min, and 72.09% in 30 min, with an apparent rate constant of 0.0131 min⁻¹, substantially outperforming the individual components (58.55% for g-C₃N₄, 58.63% for Zn_0.8Cd_0.2S, and 70.15% for Cu₃P within 180 min). The improved photocatalytic capability of Cu₃P/Zn_0.8Cd_0.2S/g-C₃N₄ is mainly attributed to the construction of a dual Z-scheme heterojunction between g-C₃N₄, Zn_0.8Cd_0.2S, and Cu₃P, promoting both the separation and movement of photoexcited charge transporters. This study demonstrates the potential of developing Cu₃P/Zn_0.8Cd_0.2S/g-C₃N₄ heterojunction as a noble-metal-free and cost-effective photocatalyst for wastewater treatment, suggesting its applicability for other purposes such as water splitting, CO₂ reduction, and antibacterial activity.