The partial oxidation of propene to acrylaldehyde on an inert gold electrode was studied at 350-450 degrees C in an electrochemical membrane reactor using (CeO2)(0.8)(SmO1.5)(0.2) as a solid electrolyte. This material has a high ionic conductivity at low temperatures. On applying a direct current to the reaction cell, acrylaldehyde was formed at the gold anode. The formation rate of acrylaldehyde increased linearly with increasing current density. It is likely that propene was oxidized to acrylaldehyde by the oxygen species produced electrochemically at the triple phase boundary of the gold-electrolyte-gas phase. These results indicate that (CeO2)(0.8)(SmO1.5)(0.2) is an attractive candidate for use in an electrochemical reactor for the partial oxidation of propene to acrylaldehyde at relatively low temperatures.