The thermodynamics of the oxidation and reduction of a series of zirconia- and alumina-supported iron-oxide catalysts were measured using coulametric titration and then compared to their activity for the water-gas shift (WGS) reaction. For the supported iron oxide catalysts with weight loadings of 5-30 wt%, the Gibbs free energy for the phase transition between Fe2O3 and Fe3O4 decreased by factor of two compared to that for bulk, unsupported iron oxide. This difference in thermodynamic properties was also found to affect the WGS reaction rates, with the rates on the supported catalysts being an order of magnitude lower than that for bulk iron oxide. We propose that the differences in the thermodynamic properties of the supported and unsupported catalysts are due to lattice strain in the supported iron oxide resulting from interactions at the FeOx-support interface. (C) 2009 Elsevier B.V. All rights reserved.