A systematic study of the photocurrent activity and the nanostructure of a TiO2 indium tin oxide (ITO) electrode prepared using reactive sputtering was carried out. The photocurrent was measured in 0.1 M NaClO4 aqueous solution using an amperometric method under irradiation. The total conversion efficiency (epsilon(eff)) was estimated. Various photoelectrode TiO2 films were synthesized by controlling deposition times, sputtering powers, total pressures, and the mole percentage of oxygen used in reactive sputtering. The physical properties of the TiO2 film such as the crystal phase, particle size, bandgap energy, and thickness were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, and profilometry. The results indicated that the optimal photocurrent was obtained at a thickness of approximately 1.2 mum and mean particle size of approximately 50 nm. The (112)-preferred orientation anatase shows higher photocurrent than (101)-orientation anatase due to its regular columnar structure. The phase diagram of the prepared TiO2 film defined by sputtering power and total pressure was also studied. (C) 2004 The Electrochemical Society.