Effect of the solution acidic-basic property on the structure and photocatalytic performance of hydrothermally-synthesized TiO2

• Phase, shape and size-tunable hydrothermal synthesis of TiO 2 in different solutions. • The photocatalytic activities are H 2 O-TiO 2 > HAc-TiO 2 > HCl-TiO 2 > NaOH-TiO 2 . • The underlying reasons for the photocatalytic activity disparity were proposed. • Helpful for future synthesis of TiO 2 -based photocatalysts by hydrothermal method. The effect of the solution acidic-basic property on the structure and photocatalytic performance of hydrothermally-synthesized TiO 2 was investigated. It was found that the solution acidic-basic property influenced the phase, morphology and size of the obtained products. Anatase TiO 2 nanoparticles, anatase TiO 2 nanoparticles, and rutile TiO 2 nanorods were synthesized in deionized water, 1.818 mol/L HAC, and 1.818 mol/L HCl aqueous solution, respectively, but phase-pure TiO 2 cannot be synthesized in 1.818 mol/L NaOH aqueous solution. For photocatalytic reduction of aqueous Cr(VI) under Xe lamp irradiation, the TiO 2 synthesized in deionized water (H 2 O-TiO 2 ) demonstrated the best photocatalytic activity. The smallest grain size, biggest specific surface area, most surface hydroxyl groups and highest photogenerated charge separation efficiency may be responsible for the greatest photocatalytic activity of H 2 O-TiO 2 . Considering that hydrothermal method is most frequently used in synthesizing TiO 2 -based photocatalysts, our finding of pure water as the best solvent for hydrothermal synthesis of TiO 2 would have great significance and provide helpful guidance.