A series of TiO2 catalysts self-doped with Ti3+ were successfully synthesized by a simple one-step solvo-thermal method with low-cost NaBH4 added as a reductant. During NaBH4 reduction, large amounts of NaBO2 and carbonaceous impurities covered the surface of the TiO2 self-doped with Ti3+, resulting in an inhibition of visible-light absorption and photocatalytic activity. In the preparation, HCl solution was used to wash off the by-product NaBO2 and carbonaceous impurities coated on the surface of the catalysts. The samples were characterized by XRD, UV-DRS, ESR, XPS, and FT-IR analyses. After HCl washing, the photocatalytic activity of the Ti3+-doped TiO2 increased markedly, while the Ti3+ content remained the same. Furthermore, it was found that the visible-light photocatalytic activity of Ti3+-doped TiO2 depended on the amount of Ti3+ added, while there was no significant impact of Ti3+ doping on its UV-light photocatalytic activity. (c) 2012 Elsevier Inc. All rights reserved.