Novel Z-Scheme g-C3N4/TiO2/NiCo2O4 Heterojunctions for Efficient Photocatalytic Degradation of Rhodamine B under Visible Light Irradiation

In this study, a novel Z-scheme heterojunction based on g-C₃N₄/TiO₂/NiCo₂O₄ nanocomposite was synthesized using a combination of hydrothermal and ultrasonic methods and investigated the photocatalytic degradation of Rhodamine B (RhB) dye. The synthesized nanocomposite was characterized XRD, FT-IR, FE-SEM, TEM, EDS, PL, UV–Vis DRS techniques. Subsequently, various parameters such as the effect of NiCo₂O₄ amount in the composite structure, pH, initial pollutant concentration, photocatalyst dosage, and different scavengers were investigated to determine the exact mechanism of the photocatalytic process. In different concentrations of NiCo₂O₄, the base value (X: 1) was determined as the optimal value in photocatalytic degradation. g-C₃N₄/TiO₂/NiCo₂O₄ composite had the highest percentage of 99.5% Rh.B dye degradation in 60 min. In addition, by examining the pH, it was found that its optimal value is 7, and the rate of dye degradation in this condition is more than other materials, and the rate constant value is 0.069 min^–1. In addition, the g-C₃N₄/TiO₂/NiCo₂O₄ catalyst showed good performance for each reuse and retained about 82% of its initial photocatalytic activity after 5 cycles. The results indicate that photoinducd (RhB) holes play a crucial role in the photocatalytic degradation of RhB in the presence of the g-C₃N₄/TiO₂/NiCo₂O₄ nanocomposite via pair Z-scheme system. In the Z-scheme system, the rapid recombination between the hole-electron pair is not observed due to the electron trapping effect of the needle-shaped NiCo₂O₄ structure, resulting in high photocatalytic efficiency and dye degradation. Therefore, Z-scheme systems are efficient and effective for the removal of water pollutants.