Production of H₂ fuel from photocatalytic splitting of water is one of the most demanding research studies in terms of sustainable development in the energy sector. In our quest to find an effective photocatalyst for H₂ production, we prepared graphene quantum dots/TiO₂-based nanocomposites using a simple hydrothermal method and studied the effect of varying morphologies of TiO₂ on photocatalytic H₂ production. The crystal structure, morphology, surface, and optical properties were thoroughly studied by using X-ray diffraction and different spectroscopic and electron microscopic techniques. The outcome of the comparative study by using various graphene quantum dots/TiO₂ nanocomposites found that P-25 TiO₂-based nanocomposite gives the highest rate of H₂ production among all with 29,548 μmol g^–1 h^–1 and is almost 14 times efficient compared to pristine P-25 TiO₂. It was also evident from the characterization results that the morphology and biphasic nature of TiO₂ play a crucial role in H₂ production. The plausible reaction mechanism explained the dual role (cocatalyst and sensitizer) of graphene quantum dots on TiO₂ nanoparticles and beneficial properties of biphasic TiO₂ as an efficient charge transfer mechanism. The prepared photocatalysts also exhibited good stability, which was examined for four cycles with a time period of 4 h, making them feasible candidates for practical applications in the future.