Highly efficient TiO 2 –graphene nanocomposite for methylene blue decomposition under visible-light irradiation

Abstract Methylene blue (MB) as a persistent dye poses serious environmental threats, requiring efficient removal methods. In the present study, the TiO₂-graphene nanocomposites have been fabricated for MB decomposition under visible-light irradiation. The graphene oxide (GO) was synthesized using the modified Hummers method and was doped on the pure TiO₂ with different amounts of 5-75 wt.% using hydrothermal method. The obtained nanocomposites were characterized using the FTIR, SEM, TEM, BET, XRD, and PL techniques. The photocatalytic activity of TiO₂-reduced graphene composites for the oxidation of MB is relatively higher than those of pure TiO₂. The nanocomposite containing the optimal 50% reduced GO exhibits the highest catalytic activity, achieving nearly complete degradation in less than 10 minutes. The incorporation of oxygen-functionalized reduced graphene oxide into mixed-phase TiO₂ (comprising both anatase and rutile) enhances the adsorption surface area, reduces the band gap, and suppresses electron-hole recombination. The kinetic of MB degradation was described by the pseudo-first-order model with a high-rate constant.