This work presents a solid-state ionic-based device to selectively detect C₂H₄ in car exhaust gases. The sensor consists of 8YSZ as the electrolyte and two electrodes: Fe_0.7Cr_1.3O₃/8YSZ and LSM/8YSZ. The main aim of this work is to optimize the catalytic behavior of the working electrode to C₂H₄ and reduce cross-sensitivity toward CO and H₂O. Several catalyst nanoparticles were infiltrated to tailor C₂H₄ adsorption and electrochemical oxidation properties while diminishing adsorption and conversion of other gas components such as CO. The infiltrated metal catalysts were selected, taking into account both adsorption and redox properties. Infiltration of Ti or Al, followed by a second infiltration of Ni, enabled the selective detection of C₂H₄ with low cross-sensitivity toward CO and H₂O in a moist gas environment. Further insight into potentiometric C₂H₄ sensing is achieved by electrochemical impedance analysis of the electrodes activated with bifunctional catalysts.