Synergistic effects of C–Cr codoping in TiO2 and enhanced sonocatalytic activity under ultrasonic irradiation

C and Cr co-doped TiO2 (C–Cr–TiO2) sonocatalyst were synthesized by doping TiO2 with glucose and CrCl3 in a sol–gel method. The samples were characterized by X-ray diffraction, transmission electron microscopy, ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, and X-ray photoelectron emission spectroscopy (XPS). C and Cr were detected by XPS analysis. The influence of dopants on the properties and sonocatalytic activity of TiO2 was studied. The sonodegradation products of methylene blue were analyzed by UV–vis absorption spectroscopy. The presence of C–Cr–TiO2 catalysts substantially enhanced the sonocatalytic degradation of MB in aqueous suspensions. The possible sonocatalytic mechanisms were also discussed.