Improved photoelectrochemical properties of TiO2-graphene nanocomposites: Effect of defect induced visible light absorption and graphene conducting channel for carrier transport

Abstract

Use of heterojunctions between two materials having favorable optical and electronic properties can lead to increased photon absorption and charge separation resulting in enhanced photo-electro-chemical energy conversion. In the present study, graphene monolayer nano-flakes are mixed with TiO2 nanoparticles to form nanocomposites having different weight percentages of graphene. The microstructural, morphological and structural properties of the composite samples are investigated using X-ray diffraction, Raman spectroscopy and transmission electron microscopy techniques. Raman studies carried out on samples annealed at different temperatures show the interfacial interaction between TiO2 and graphene, although Anatase TiO2 and graphene maintain their phase integrity. PEC measurements show higher photo-electro-chemical activity in TiO2-graphene nanocomposite at an optimized concentration (2.0 weight percent) due to increased surface area, higher optical absorption in the visible part of the solar spectrum and favorable carrier transport due to increased concentration of defect states and graphene acting as a charge carrier medium.

Keywords

• Sustainable energy
• Photoelectrochemical effect
• Nanocomposites
• Monolayered graphene
• Titania nanoparticles
• Defect states