Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (06): 1487-1492.doi: 10.3866/PKU.WHXB20110621

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Structure, Surface Properties and Photocatalytic Activity of TiO2 and TiO2/SiO2 Catalysts Prepared at Different pH Values

QIU Wei, REN Cheng-Jun, GONG Mao-Chu, HOU Yun-Ze, CHEN Yao-Qiang   

  1. Key Laboratory of Green Chemistry & Technology of the Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
  • Received:2011-02-25 Revised:2011-04-11 Published:2011-05-31
  • Contact: REN Cheng-Jun, CHEN Yao-Qiang E-mail:renchengjun@scu.edu.cn. nic7501@scu.edu.cn

Abstract:

TiO2 and SiO2-doped TiO2 (TiO2/SiO2) catalysts were prepared using aqueous solutions containing a TiOSO4 and/or SiO2 sol in which NH3·H2O was used to adjust the pH value by a precipitation method. The as-synthesized photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption (BET), UV-Vis diffuse reflectance spectroscopy, NH3 temperature programmed desorption (NH3-TPD), and Fourier transform infrared (FT-IR) spectroscopy. The XRD patterns showed that anatase and rutile coexisted in the as-prepared TiO2 and the rutile phase content increased with the increase in pH value. However, only anatase-TiO2 was observed in the TiO2/SiO2 catalysts. SEM revealed that the surface morphology of the particles was a sub-spherical shape and some agglomeration occurred on the surface while the particle size was mostly between 10 and 25 nm. Surface area measurements showed that the surface areas of the catalysts increased slightly with the increase in pH value. The incorporation of SiO2 increased the surface area. NH3-TPD analysis indicated that the amount of surface acid increased as the pH increased. The amount of surface acid on SiO2-doped TiO2 was higher than that on TiO2 when they were prepared at identical pH values. The addition of silica and the high pH value environment led to more surface hydroxyl groups on the catalysts as determined by FT-IR spectroscopy. The photocatalytic activity of the catalysts improved remarkably with the increase in pH value. The photocatalytic activity of SiO2-doped TiO2 is better than that of TiO2. The TiO2/SiO2 catalyst has better durability.

Key words: pH, TiO2, SiO2-doping, Microstructure, Surface property, Photocatalysis

MSC2000: 

  • O643