The hybrid sulfur cycle has been investigated as a means to produce clean hydrogen efficiently on a large scale by first decomposing H2SO4 to SO2, O-2, and H2O and then electrochemically oxidizing SO2 back to H2SO4 with the cogeneration of H-2. Thus far, it has been determined that the total cell potential for the hybrid sulfur electrolyzer is controlled mainly by water transport in the cell. Water is required at the anode to participate in the oxidation of SO2 to H2SO4 and to hydrate the membrane. In addition, water transport to the anode influences the concentration of the sulfuric acid produced. The resulting sulfuric acid concentration at the anode influences the equilibrium potential of and the reaction kinetics for SO2 oxidation and the average conductivity of the membrane. A final contribution to the potential loss is the diffusion of SO2 through the sulfuric acid to the catalyst site. Here, we extend our understanding of water transport to predict the individual contributions to the total cell potential. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3397901] All rights reserved.