Electrochemical investigations have been carried out on Pd/YSZ catalyst-electrodes for deep oxidation of methane in excess of oxygen. A wet impregnation technique has been used to achieve highly active Pd catalyst films. It was found that co-feeding of ethylene in oxidizing gas mixtures enhances the rate of methane conversion and allows for electrochemical promotion of methane oxidation at temperatures as low as 320 degrees C. The electrochemical promotion behavior has been studied with long term potentiostatic transients together with AC impedance measurements during polarization. (C) 2012 Elsevier B.V. All rights reserved.