Incorporation of graphene quantum dots to enhance photocatalytic properties of anatase TiO 2
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esearch Letter
Incorporation of graphene quantum dots to enhance photocatalytic properties of anatase TiO2 Sowbaranigha Chinnusamy, Ravneet Kaur, Anuja Bokare, and Folarin Erogbogbo*, Department of Biomedical, Chemical, and Materials Engineering, San Jose State University, 1 Washington Square, San Jose, California 95112, USA *Address all correspondence to Folarin Erogbogbo at [email protected] (Received 9 November 2017; accepted 4 January 2018)
Abstract Different sized graphene quantum dots (GQDs) have been synthesized by an inexpensive wet chemical method using bird charcoal as a precursor. Obtained GQDs found to have luminescence and visible light absorption. These GQDs are further coupled with titanium dioxide (TiO2) to form TiO2–GQDs nanocomposites. GQD nanostructures exhibit band gap tunability and have the potential to enhance the photoabsorption in TiO2. The hybrid combination of the nanomaterials decrease the recombination of charge carriers, increase charge carrier mobility, and improve the overall photoconversion efficiency. The composites exhibit higher photocatalytic activity and rate constants value than pure TiO2.
Introduction Global energy inequality, climate change, altered carbon cycle, and fossil fuel depletion are the major driving forces for researchers and scientists to direct their attention toward replacing carbon-intensive fuels with renewable energy sources. Solar energy is clean and abundantly available renewable energy, to earth receiving nearly 2 kW/h.[1] However, fabrication of solar cells or solar-storage devices is often associated with the high costs and low conversion efficiencies, which are the main limitations for scaling up this technology. Hence, in the present scenario, efficient and cost-effective conversion of solar energy into an electricity and fuel is the real challenge.[2] Among all the photoactive materials, titanium dioxide (TiO2) is the most widely used photocatalyst due to its optoelectronic properties, stability, low cost, and non-toxicity.[3–5] However, its large band gap (3.2 eV) and high rate of electron–hole recombination limit its efficiency only up to the ultraviolet (UV) light region.[6] Recently, composites of carbon materials [carbon nanotubes, graphene, and graphene quantum dots (GQDs)] with TiO2 are attracting significant attention in this area, because these systems harvest a broad spectrum of solar light and exhibit fast charge separation as compared with pristine TiO2.[7–10] Compared with two-dimensional graphene–nonosheets and one-dimensional nanoribbons, zerodimensional GQDs have discrete electronic levels, allowing for hot electron injection and efficient charge separation. In addition to that, GQD extended π-electron systems can be put in direct contact with a TiO2 surface, facilitating the donor– acceptor contact.[11–14] Therefore, in the present study, coupling GQDs with TiO2 has been attempted to improve the charge-separation and visible light absorption of the TiO2.
The present paper reports the synthesis of GQDs using a very inexpensive an
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