Highly selective zirconia-based propene sensor attached with sol-gel derived NiO nanospheres

Nanospheres of nickel oxide (NiO) were synthesized by a simple modified sol-gel route using nickel nitrate as a precursor and citric acid as a gelling agent. An yttria-stabilized zirconia (YSZ)-based sensor was fabricated using the sol-gel derived NiO nanospheres as the sensing electrode (SE) and Pt as the reference electrode (RE), and its sensing characteristics were examined in the temperature range of 650-800 degrees C under various O-2 concentrations (5, 10, 15 and 21 vol%). The fabricated NiO-SE was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It turned out that the sensor attached with the sol-gel derived NiO-SE exhibited a selective and sensitive response to propene (C3H6) at 700 degrees C in all measured O-2 concentrations. The sensor showed the highest sensitivity and selectivity to propene in 21 vol% O-2. In addition, the sensor exhibited a stable response to C3H6 for about two months. The sensing mechanism was confirmed to be mixed-potential-type. It is believed that the nanofeatures associated with the sol-gel derived NiO seemed to be responsible for the high sensitivity and selectivity to C3H6.