The main objective of this study was to prepare effective photocatalysts for splitting of seawater for solar fuel - H-2 and degradation of seawater organic pollutants such as dyes. To enhance photocatalytic activities, CuO is supported on nano TiO2 (CuO/nano TiO2). By X-ray absorption near edge structure (XANES) spectroscopy, CuO clusters are found on nano TiO2. The 2.5% CuO/nano TiO2 has greater activities in photocatalytic splitting of water and seawater than nano TiO2 by 9.9 and 7.8 times, respectively. Interestingly, the 2.5% CuO/nano TiO2 is also very active for photocatalytic splitting of water and seawater contaminated with dyes such as methylene blue (MB) (10 ppm). Under a 5-h irradiation of the UV-Vis light, about 99% of MB is degraded while 3.1 mu mol/h g cat of H-2 are generated from seawater in the photocatalysis process. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.