Ex Situ Fabrication of the G–TiO₂ Nanocomposite with Tunable Physiochemical Characteristics for Enhanced Photocatalytic Performance

This study reports fabrication of graphene-titanium dioxide (G-TiO₂) nanocomposites with varying graphene content (0%, 25%, 50%, and 75%) through a sonication-assisted co-precipitation method. The synthesized materials were analyzed through FTIR, DRS, SEM, and XRD techniques, which confirmed the successful formation of an anatase-phase TiO₂ tetragonal structure with crystallite sizes ranging from 10 to 25 nm after calcination at 600 °C for 4 h. The addition of graphene resulted in a significant reduction in the TiO₂ bandgap energy from 3.2 eV to 1.55 eV, enhancing the material's absorption in the visible-light spectrum. The nanocomposite with 50% graphene loading exhibited strong adsorption and the highest photocatalytic efficiency, achieving 98.29% degradation of cationic methylene blue dye under visible-light irradiation. This exceptional performance is attributed to the synergistic effects of graphene, including improved light absorption, enhanced charge carrier separation, and increased electron transfer efficiency. Kinetic analysis revealed that the photocatalytic degradation followed pseudo-first-order reaction kinetics. Furthermore, recycling tests demonstrated the structural stability and reusability (up to 5 cycles) of the nanocomposite, indicating its potential as an effective photocatalyst for environmental applications. The effectiveness of G-TiO₂ in mitigating industrial pollutants also underscores the significance of the sonication-assisted co-precipitation approach.