CuO/ZnO composite films with different atomic Cu/Zn ratios were for the first time fabricated on indium tin oxide (ITO)-coated glass substrates via a cathodic co-electrodeposition route from baths containing Zn(NO3)(2) and Cu(CH3COO)(2). The obtained composite films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Hexavalent chromium (Cr(VI)) was used as a model pollutant to evaluate their photocatalytic activity. For a bath containing Zn(NO3)(2) with a certain concentration, the concentration of Cu2+ ions added into this bath play an important role in fabrication of CuO/ZnO composite films. When the Cu2+ concentration in a bath is lower, the obtained composite is a Cu-doped ZnO film. The electrodeposited CuO/ZnO composite films show higher photocatalytic activity towards reduction of Cr(VI) compared to pure ZnO both under UV and under UV-vis light illumination. Furthermore, the photocatalytic activity of CuO/ZnO composite films is related to their atomic Cu/Zn ratios. The mechanism of CuO/ZnO composite films for improvement in photocatalytic activity was also discussed. (C) 2010 Elsevier B.V. All rights reserved.