The electrochemically promoted induction of self-sustained catalytic rate and potential oscillations during C2H4 oxidation was studied over sputtered Rh thin (40 nm catalyst. lms interfaced with ZrO2 (8 mol% Y2O3). The reaction rate oscillates simultaneously with the catalyst potential, and always in the opposite direction. The electrochemically induced oscillatory rate is typically 60 times larger than the open-circuit catalytic rate and 1000 times larger than the electrochemical rate of O2- supply to the catalyst. The phenomenon is completely reversible and only observed under anodic polarization where the rate oscillates between the values corresponding to metallic Rh and surface Rh2O3. The oscillations are caused by the electrochemically controlled backspillover of O2- to the catalyst surface and the concomitant, via repulsive lateral interactions, decomposition of surface rhodium oxide followed by surface reoxidation to Rh2O3 by gaseous O-2.