Decoration of Graphene Quantum Dots on TiO2 Nanostructures: Photosensitizer and Cocatalyst Role for Enhanced Hydrogen Generation

Production of H-2 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 H-2 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 H-2 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 H-2 production among all with 29,548 mu mol 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 H-2 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.