The Ni/CeO(2) catalysts with different calcination temperatures have been tested for hydrogen production in sulfur-iodine (SI or IS) cycle. TG-FTIR, BET, XRD, HRTEM and TPR were performed for catalyst characterization. It was found that the Ni(2+) ions could be inserted into the ceria lattice. This brought about the strong interaction between Ni and CeO(2) and the generation of oxygen vacancies. Perfect crystallites were formed in the catalysts. It was evident that there was a change in particle size and morphology as the calcination temperature increased from 300 to 900 degrees C. The Ni/CeO(2) catalysts with different calcination temperatures showed better catalytic activity by comparison with blank yield, especially Ni/Ce700. A hypothetic mechanism of HI catalytic decomposition on Ni/CeO(2) has been constructed. The two important reactive sites were assumed for HI catalytic decomposition. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.