The nonfaradaic electrochemical promotion modification of catalytic activity (NEMCA) was investigated in the total oxidation of propane and propene on Pt films deposited on 8 mol% Y2O3-stabilized ZrO2 solid electrolyte. It was found that propane and propene oxidation exhibit opposite behaviors with respect to the applied overpotentials. Propane oxidation exhibits an electrophobic enhancement (reaction increases upon positive polarization of the catalyst-electrode) while propene oxidation is electrophilic. Upon applied negative overpotential and under an oxygen-rich atmosphere, the rate of propane oxidation strongly decreases, with high values of faradaic efficiency, up to 10,000. Propane and propene oxidation rates were found to be controlled over a wide range of voltage in a reversible way. Catalytic activity measurements under open-circuit voltage conditions, using solid electrolyte potentiometry and temperature-programmed desorption, have been used in order to understand and investigate the origins of this electrochemical promotion. They seem related to different behaviors of propane and propene with respect to their competitive adsorption with oxygen on platinum. Propene adsorbs strongly in competition with oxygen, whereas propane adsorbs weakly. This indicates that the NEMCA behavior of a catalytic reaction is dependent on the oxygen coverage on the catalyst-electrode under open-circuit conditions.