Synthesis of a TiO ₂ –CuO@rGO Ternary Nanocomposite for Effective Photocatalytic Treatment of the Methylene Blue Dye

An efficient TiO₂-CuO@rGO ternary nanocomposite (NC) was designed and synthesized using an environmentally benign strategy involving ascorbic acid-assisted reduction of graphene oxide (GO) followed by a one-pot hydrothermal assembly of CuO and TiO₂. The green and surfactant-free fabrication route represents a key methodology over traditional hydrazine-based or multistep processes. The fabricated materials were characterized for their morphology, composition, crystallinity, net surface charge, functional groups, thermal stability, and optical properties through selected analytical techniques such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, pH_pzc, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and ultraviolet-visible spectroscopy (UV-vis). Furthermore, the photocatalytic degradation capability of the as-prepared NCs was assessed to eliminate the methylene blue (MB) dye from wastewater under different experimental conditions. The TiO₂-CuO@rGO ternary nanocomposite demonstrates superior degradation efficiency compared to its binary counterparts. The experiments were conducted using 0.03 g of the catalyst in a 100 ppm MB solution at pH 7 and 30 °C, under UV-vis-light irradiation for 80 min. The degradation process was analyzed using various kinetic and thermodynamic models. Kinetic data revealed that the photocatalytic degradation follows a pseudo-second-order model, indicating a synergistic adsorption-photocatalysis mechanism. Thermodynamic parameters confirmed the endothermic and spontaneous nature of the reaction, while recycling tests demonstrated excellent operational stability over multiple cycles. The enhanced activity is attributed to the p-n heterojunction between CuO and TiO₂, effective charge separation via rGO, reduced bandgap energy, and improved visible-light energy. These results establish the ternary NCs as a robust, reusable, and environmentally sustainable photocatalyst with strong potential for real-world wastewater treatment.