Different amounts of Co-doped TiO2 powders and thin films were prepared by following a conventional co-precipitation and sol-gel dip coating technique, respectively. The synthesized powders and thin films were subjected to thermal treatments from 400 to 800 degrees C and were thoroughly investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive analysis with X-rays, FT-infrared, FT-Raman, diffuse reflectance spectroscopy, ultraviolet visible spectroscopy, BET surface area, zeta potential, flat band potential measurements, band-gap energy, etc. The photocatalytic ability of the powders was evaluated by methylene blue (MB) degradation studies. The thin films were characterized by photocurrent and ultraviolet-visible (UV-Vis) spectroscopy techniques. The characterization results suggest that the Co-doped TiO2 powders synthesized in this study consist mainly anatase phase, and possess reasonably high specific surface area, low band gap energy and flat band potentials amenable to water oxidation in photoelectrochemical (PEC) cells. The photocatalytic degradation of MB over Co-doped TiO2 powders followed the Langmuir-Hinshelwood first order reaction rate relationship. The 01 wt.% Co-doped TiO2 composition provided the higher photocurrent, n-type semi-conducting behavior and higher photocatalytic activity among various Co-doped TiO2 compositions and pure TiO2 investigated. (C) 2012 Elsevier B.V. All rights reserved.