Hydrothermal Synthesis of Ionic Liquid [Bmim]OH-Modified TiO2 Nanoparticles with Enhanced Photocatalytic Activity under Visible Light

TiO2 nanocomposites modified with the ionic liquid [Bmim]OH are synthesized by a hydrothermal procedure. X‐ray diffraction, Zeta‐potential measurement, TEM, thermogravimetric analysis, photoluminescence, UV/Vis, FTIR, and X‐ray photoelectron spectroscopy are used to characterize the TiO2 nanocomposites. The TiO2 nanocomposites consist of pure anatase particles of about 10 nm. The modification of [Bmim]OH on the surface of the TiO2 particles extends the TiO2 absorption edge to the visible‐light region. The electrochemical redox potentials indicated that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of [Bmim]OH match well with the valence band (VB) and conduction band (CB) of the TiO2 semiconductor. [Bmim]OH‐modified TiO2 is much more active than pristine TiO2 under visible‐light irradiation in the photocatalytic degradation of methylene blue in aqueous solution. [Bmim]OH is chemically bonded to the surface TiOH of TiO2 particles rather than adsorbed on the surface. A possible mechanism for the photocatalysis is proposed. Visible response: [Bmim]OH‐modified TiO2 nanocomposites synthesized by a hydrothermal procedure show significantly higher photocatalytic performance in the degradation of methylene blue under visible‐light irradiation than pure TiO2. The characterization results reveal that [Bmim]OH are probably bonded to the surface TiOH groups of the TiO2 particles rather than adsorbed on the surface.