Significant amounts of hydrogen or oxygen can be generated at moderate temperatures (500-900 degrees C) if a mixed-conducting (i.e., electron- and ion-conducting) membrane is used to remove either oxygen or hydrogen as it is generated. We demonstrated this in a previous study using cermet (i.e., ceramic-metal composite) membranes composed of an oxygen ion conductor, Gd-doped CeO2 (CGO), and an electronic conductor, Ni. In the present study, we show several ways to increase the hydrogen production rate by water dissociation with mixed-conducting membranes. Producing CGO/Ni membranes with a finer microstructure enlarged the triple-phase-boundary area, and increased the hydrogen production rate to approximate to 10 cm(3)(STP)/ min-cm(2). Using a single-phase, mixed-conducting membranes [SrFeCo0.5Ox(SFC2)] also produced higher hydrogen production rates, relative to dual-phase cermet membranes. ((c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.