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

Abstract

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.

Graphene Quantum Dots Decorated TiO2 Nanostructures: Sustainable Approach for Photocatalytic Remediation of an Industrial Pollutant

“…[34][35][36] The derived GQDs show unique optical properties due to disordered structures and defect sites which has been explained in detail in our previous study. [37] In this study, we have extended the application of the efficient photocatalyst composed of varied percentage of "metal free" GQDs decorated TiO 2 , previously reported by our research group, [23] as a means of employing a sustainable approach for the application of photocatalytic degradation of industrial pollutants, [36][37] in this case, MB under visible-light. Amidst different compositions GQDs incorporated TiO 2 nanostructures, the photocatalytic system comprising of TiO 2 nanotubes and 2 wt% GQDs were found to display a degradation efficiency of 96.7 % towards MB under visible light irradiation of 120 min.…”

Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

“…[145][146][147] In fact, the GQDs composites are more efficient and popular photocatalysts in which the GQDs serves as the visible light photosensitizers. For example, Raghavan et al [148] reported the synthesis of GQDs/ TiO 2 (CTNT) and GQDs/P25 (GTNP) composite photocatalysts via the hydrothermal route and investigated the effect of TiO 2 morphology varying on the performance of the photocatalyst for H 2 evolution. The TEM and HRTEM micrographs of CTNP composite are revealed in Figure 6A,B.…”

“…According to the suggested mechanism Reproduced with permission. [148] Copyright 2020, The American Chemical Society.…”

“…C) Photocatalytic activities for H 2 evolution over the CTNT composites and D) over the CTNP composites. E) Sensitization role of the GQDs in the composite and F) cocatalyst role of the GQDs in the composite.Reproduced with permission [148]. Copyright 2020, The American Chemical Society.…”

Rhus Semialata Derived Carbon Quantum Dots Decorated Pt Deposited TiO2 for Efficient Light‐Driven Hydrogen Production

“…CDs/KNbO 3 photocatalytic system was reported by Qu et al., [33] wherein CDs played the role of a co‐catalyst and the composite system exhibited excellent photocatalytic activity with concomitant evolution of hydrogen. In our earlier research, we also reported on graphene quantum dots (GQDs) based TiO 2 nanocomposites for photocatalytic production of hydrogen and discovered that GQD incorporation led to a smaller band gap and improved hydrogen evolution in comparison to that of the commercial, P‐25 TiO 2 nanoparticles [34] . Munevver tuna genc et al., reported CQDs/TiO 2 nanocomposite as photocatalysts for hydrogen production activity under visible light (>420 nm) wherein CQDs were derived from a green biomass source ‘‘Gingko Biloba‘‘.…”