A comparative study of photocatalytic splitting of water into hydrogen and oxygen over NiO and TiO2 was carried out using 355 nm laser radiations as a light source. The effect of dissolved metal ions on photocatalytic splitting of water over these catalysts was also studied by using Fe3+. Ag+ and Li+ ions to enhance the efficiency of the process by suppressing the non-productive electron-hole recombination. The dependence of products yield on incident laser energy, amount of catalyst (particle density), stirring rate and laser beam diameter was also investigated for activity comparison of these catalysts. It was demonstrated for the first time that by using a high photon flux source such as laser, the problems of longer exposure time and low photonic efficiencies could be resolved which is common problem with conventional UV lamp based photocatalysis. (C) 2004 Elsevier B.V. All rights reserved.