The sensing characteristics of a yttria-stabilized zirconia (YSZ)-based sensor using a sensing electrode (SE) consisting of rod-shaped TiO2 added with 1 wt.% of nano-sized Pd particles (abbreviated as TiO2(+Pd)-SE) were evaluated, aiming at selective detection of hydrocarbons. The rod-shaped TiO2-SE without Pd addition (TiO2-SE) was found to give high sensitivities to both C3H8 and C3H6 which were used as representatives of alkane and alkene groups, respectively, in hydrocarbons (HCs), while TiO2(+Pd)-SE gave selective detection of C3H8. The evaluation of catalytic activity to the gas-phase oxidation of HCs for the SE materials revealed that the oxidation of C3H6 was largely promoted by the Pd addition, leading to the high selectivity to C3H8 for the sensor using TiO2(+Pd)-SE. From the results of polarization-curve measurements, the current value for the cathodic reaction of O-2 was found to be slightly decreased by the Pd addition, while those for the anodic reaction of C3H8 and C3H6 were largely decreased. This is presumably due to the decrease in the actual concentration of C3H8 and C3H6 at the SE/YSZ interface owing to the promoted gas-phase oxidation of these HCs through the TiO2(+Pd)-SE layer. XRD measurements as well as SEM observations confirmed that the added Pd particles were existing as PdO particles on the surface of the rutile-type TiO2 rods after the SE fabrication process. The stability test revealed that the C3H8 sensitivity of the sensor using TiO2(+Pd)-SE gradually increased and reached the stable value after the 12 day operation. By considering the results of the complex-impedance analysis, we believed that this gradual increase in sensitivity was due to the decrease in the catalytic activity against the gas-phase oxidation of C3H8 in the TiO2(+Pd)-SE layer. (C) 2013 Elsevier B.V. All rights reserved.