Controlled growth of TiO2 and TiO2-RGO composite nanoparticles in ionic liquids for enhanced photocatalytic H2 generation

TiO2 nanoparticles and TiO2-RGO (reduced graphene oxide) composite were synthesized by ionothermal method at 100 and 120 degrees C for 24h using two different ionic liquids (ILs), 1-(2-methoxyethyl)-3methylimidazolium methanesulfonate (IL1) and 1-(2-methoxyethyl)-3-methylimidazolium tetrafluoroborate (IL2). BET surface area analysis of the composites showed surface areas of 170 and 161 m(2) g(-1) for TiO2 and TiO2-RGO composite respectively. TEM images show that the sizes of the particles are around 4 nm and in the composite clearly show that TiO2 NPs are present on the surface of the graphene sheet. The use of IL2 produces a high crystalline TiO2 NPs with pure anatase phase without need of thermal treatment (TT). Hydrogen generation by UV light on TiO2 NPs or TiO2-RGO composite prepared in ILs without thermal treatment (TT) show lower rate than TiO2 P25. After TT at 400 degrees C a higher H-2 production rate (up to 0.76 mmol h(-1) g(-1)) due to the increase in crystallinity was measured. The photocatalytic activity was further enhanced for TiO2-RGO composite. The electron-accepting and electron-transporting properties of graphene in the composite could indeed suppress the charge recombination and improve their photocatalytic activities. (c) 2013 Elsevier B.V. All rights reserved.