The electrochemical promotion of the CO2 hydrogenation reaction on I'd catalyst-electrode films interfaced to YSZ or beta"-Al2O3 was investigated for H-2-rich mixtures under atmospheric pressure and at temperatures 533 degrees C to 605 degrees C, where the only products were CO and H2O (reverse water gas shift reaction). In the case of Pd/YSZ, CO formation was enhanced by up to approximately 6 times by applying either negative or positive overpotentials ("inverted volcano" behavior). Rate changes by up to almost 150 times higher than the corresponding pumping rate of oxygen ions were observed. In the case of Pd/p"-Al2O3 the CO formation rate increased by supplying sodium to the catalyst. Rate increases by up to 6.7 times were observed by decreasing catalyst potential by 0.34 V. (C) 2008 Elsevier B.V. All rights reserved.