TiO2 nanoparticles coin pounded with different amounts of bismuth were prepared by a sol-gel method, and the effects of compounding bismuth on the phase transformation, photoinduced charge separation and photocatalytic activity for degrading rhodamine B solution were mainly investigated, along with enhancement mechanism of photocatalytic activity of TiO2 nanoparticles by compounding bismuth species. It can be confirmed that, by means of X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS) and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), compounding bismuth can extend the optical response, and effectively inhibit the phase transformation process from anatase to rutile, consequently greatly improving the anatase crystallinity so as to promote the photoinduced charge separation. These factors are responsible for the increase in the photocatalytic activity of TiO2 compounded with an appropriate amount of bismuth species. (C) 2008 Elsevier B.V. All rights reserved.