A modification of the conventional Sulfur-Iodine (S-I) thermochemical water-splitting cycle (TWSC) by means of double exchange reactions (metathesis) is presented. In conventional S-I TWSC an excess of water and iodine has to be used for phase separation and a large amount of heat is requested for water and iodine evaporation. To reduce the amount of these chemicals we propose the formation of solid phases obtained by using lead as the precipitating agent. The obtained solid can be easily separated from the liquid by filtration avoiding evaporation processes. The formation of anhydrous gases allows to minimize corrosion problems and to reduce heat demand during hydrogen iodide decomposition. 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.