The electrochemical promotion of C2H4 oxidation reaction has been investigated under various feed gas compositions and temperatures over a Pt/Y2O3-stabilized ZrO2 catalyst electrode. It was found that under oxidizing conditions the reaction exhibits electrophobic behavior, i.e. the catalytic rate of CO2 formation increases with anodic potential application, while it shifts to electrophilic behaviour, i.e. the rate increases with cathodic potential application, under near stoichiometric feed conditions. At intermediate C2H4 to O-2 ratios and low temperatures volcano type behavior is observed, i.e. the rate is poisoned both with anodic and cathodic potential application. The effect of feed gas composition on the electrochemical promotion behaviour is related to changes in the reaction kinetic order with respect to C2H4 and O-2. The results are in excellent agreement with the rules of electrochemical and chemical promotion.