Hydrothermal synthesis of high-efficiency Pr, N, P-tridoped TiO2 from TiCl4 hydrolysis and mechanism of its enhanced photoactivity

A hydrothermal method without post-calcination was successfully developed to obtain high-efficiency Pr, N, P-tridoped anatase-TiO2 (PrNPTO) nano-photocatalyst based on TiCl4 hydrolysis in aqueous solution. The samples were characterized by X-ray diffraction, transmission electron microscopy, N-2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, thermogravimetry and differential thermoanalysis, UV-vis absorbance spectroscopy, and photoluminescence spectroscopy measurements. Results showed that among as-synthesized undoped and doped samples, PrNPTO presented the highest photoactivity for 4-chlorophenol (4-CP) degradation under simulated sunlight irradiation (K-app = 0.0603 min(-1)), which was 5.15 times that of commercial P25 TiO2 (K-app = 0.0117 min(-1)). TOC removal rate for 4-CP solution (20 mg L-1) in the presence of PrNPTO (0.8 g L-1) reached 76.9% after 120 min irradiation, indicating that 4-CP was mineralized efficiently. Radical scavenging experiments indicated that (OH)-O-center dot in the solution was main reactive species, but photogenerated electrons also played a minor role by finally transformed (OH)-O-center dot. Enhanced photoactivity of PrNPTO was attributed to the increased UV light absorption, reduced photogenerated e /h(+) recombination, higher surface hydroxyl content, as well as improved surface textural properties. PrNPTO was reused many times without obvious diminution of photoactivity, which extends the practical application of TiO2. (C) 2014 Elsevier B. V. All rights reserved.