Effect of surfactant concentration on active species generation and photocatalytic properties of TiO2

The importance of varying surfactant concentration in TiO2 synthesis and its effect on the formation of OH radical, oxygen vacancy, and photocatalytic properties is the focus of this work. The sol-gel method was adopted in the synthesis of TiO2 nanoparticles and calcined in air/argon at 400 degrees C. In a typical synthesis, the concentration of non-ionic surfactant, pluronic F127, was varied by mass relative to the concentration of TiO2 precursor. The as-prepared materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), N-2 sorption, Raman spectroscopy, fluorescence spectrometry, and electron spin resonance spectroscopy (ESR). Photocatalytic properties of the materials were evaluated by monitoring the decoloration of 10mg/L model dye, methylene blue at pH 3, 7, and 11 in the presence of different light sources. Pore size distribution calculated from the Barrett-Joyner-Halenda (BJH) shows that the materials are both meso- and macro-porous with surface area of 48-110cm(2)/g. The as-prepared TiO2 nanoparticles existed in the anatase phase with a decrease in crystal size as the concentration of the surfactant used in synthesis increased. An increase in OH radical and surface oxygen vacancy formation was also observed as the concentration of surfactant used in synthesis increased. The as-prepared TiO2, calcined in air and argon, T-1:S(3)AA,showed the best photocatalytic activity resulting from its relatively higher hydroxyl radical generated and surface oxygen vacancy. (C) 2015 Elsevier B.V. All rights reserved.