The rate of complete propylene oxidation on polycrystalline Pt films deposited on 8 mol% Y2O3-stabilized-ZrO2 (YSZ), an O2-conductor, can be reversibly enhanced by up to a factor of 6 by varying the potential of the Pt catalyst film. The reaction rate increase is typically 2000 times higher than the electrochemically controlled rate of oxygen removal from the Pt catalyst surface. Electrochemical supply of promoting oxide ions does not affect significantly the catalytic rate. The catalytic reaction activation energy varies linearly by a factor of 4 with varying catalyst potential, leading to the appearance of the compensation effect. The observed pronounced promotional phenomena are discussed in view of the reaction mechanism, previous electrochemical promotion studies, and recent TPD and XPS investigations.