Mesoporous anatase TiO2 nanopowder was synthesized by hydrothermal method at 130 C for 12 h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), HRTEM, and Brunauer-Emmett-Teller (BET) surface area. The as-synthesized sample with narrow pore size distribution had average pore diameter about 3-4 nm. The specific BET surface area of the as-synthesized sample was about 193 m(2)/g. Mesoporous anatase TiO2 nanopowders (prepared by this study) showed higher photocatalytic activity than the nanorods TiO2, nanofibers TiO2 mesoporous TiO2, and commercial TiO2 nanoparticles (P-25, JRC-01, and JRC-03). The solar energy conversion efficiency (n) of the cell using the mesoporous anatase TiO2 was about 6.30% with the short-circuit current density (Jsc) of 13.28 mA/cm(2), the open-circuit voltage (Voc) of 0.702 V and the fill factor (ff) of 0.676; while n of the cell using P-25 reached 5.82% with Jsc of 12.74 mA/cm(2), Voc of 0.704 V and ff of 0.649. (c) 2007 Elsevier Ltd. All rights reserved.