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

•TiO2 and TiO2–RGO (reduced graphene oxide) nanoparticles (NPs) are prepared in ionic liquids (ILs).•The IL promotes the reduction of graphene oxide (GO) to RGO.•In IL highly crystalline TiO2 NPs with pure anatase phase without need of thermal treatment.•The TiO2–RGO hybrid material is high active photocatalyst for hydrogen generation.

TiO2 nanoparticles and TiO2–RGO (reduced graphene oxide) composite were synthesized by ionothermal method at 100 and 120 °C for 24 h using two different ionic liquids (ILs), 1-(2-methoxyethyl)-3-methylimidazolium methanesulfonate (IL1) and 1-(2-methoxyethyl)-3-methylimidazolium tetrafluoroborate (IL2). BET surface area analysis of the composites showed surface areas of 170 and 161 m2 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 °C a higher H2 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.

Graphical abstractTiO2 and TiO2–RGO composite nanoparticles were successfully prepared by ionothermal method using two different ionic liquids (ILs), 1-(2-methoxyethyl)-3-methylimidazolium methanesulfonate (IL1) and 1-(2-methoxyethyl)-3-methylimidazolium tetrafluoroborate (IL2). The use of IL2 produces a high crystalline TiO2 NPs with pure anatase phase without need of thermal treatment. The photocatalytic activity of TiO2–RGO was much better compared to TiO2-P25 and TiO2 nanoparticles.Figure optionsDownload full-size imageDownload high-quality image (174 K)Download as PowerPoint slide