One potential solution to reduce the greenhouse gas emission is the generation of fuels through thermochemical dissociation of CO2 and H2O. Previous studies have shown that non-stoichiometric CeO2-d oxide had the capacity to dissociate these two fluids at high temperature (900°C) (1) while reduction of CeO2 to CeO2-d was performed at higher temperature (1600°C) (2), energy being provided by solar energy. One issue is the high temperature which (2) occurs. With this in mind Nb-substituted ceria CeNbO4 has been studied and reduction of CeNbO4+d to CeNbO4 occurs readily reducing energy costs. This reduction occurs at lower temperature under air and hence the reduction of H2O over CeNbO4 is of interest. The purpose of this experiment is to heat CeNbO4 and related phases with a H2O flow and to examine the structural changes while the sample is reoxidized.