One-pot synthesis of TiO₂/graphene nanocomposites for excellent visible light photocatalysis based on chemical exfoliation method

Facile electron-hole recombination and the broad band gap are two major bottlenecks of titanium dioxide (TiO₂) applied in visible-light photocatalysis. Hybridization of TiO₂ with graphene is a promising strategy to alleviate these drawbacks. In this paper, we demonstrate a novel technique to synthesize TiO₂/graphene nanocomposites without the use of graphene oxide (GO). Graphene dispersion was obtained through the chemical exfoliation of graphite in titanium tetra-n-butoxide by ultrasonication. The dispersion was directly used for the sol-gel reaction in the presence of different catalysts, affording TiO₂/graphene nanocomposites featured with several advantages: i) the formation of a TiO₂ nano layer that uniformly and thinly covered graphene sheets, ii) a trace amount of defects on graphene sheets, iii) a significant extension of the absorption edge into the visible light region, and iv) a dramatic suppression of electron-hole recombination. When tested for methylene blue decomposition under visible light, our nanocomposites exhibited the photocatalytic activity 15 and 5 times greater than that of TiO₂-P25 and a conventional GO-based nanocomposite, respectively.