Development of Potentiometric Sensors for C(2)H(4) Detection

Gas exhaust emissions in vehicles are increasingly restrictive in EU and USA. Diesel engines are particularly affected by limitation in hydrocarbons and NOx concentrations. This work presents a screening of working electrode materials to develop a potentiometric sensor, with the most promising material to detect being C(2)H(4) at 550 °C. The device consists of a dense 8YSZ (8 mol% Y(2)O(3) stabilized ZrO(2)) disk as oxide-ion conducting electrolyte, whereas platinum is screen-printed in the back face as reference electrode. As working electrode, several materials such as Fe(0.7)Cr(1.3)O(3), ZnCr(2)O(4), Fe(2)NiO(4), La(0.8)Sr(0.2)CrO(3−δ) (LSC), La(0.8)Sr(0.2)MnO(3) (LSM), and NiO+5%wt Au were tested to detect C(2)H(4). Sensor voltage was measured for several concentrations of C(2)H(4) and CO as these are two of the major oxidizable compounds in a diesel exhaust gas. Fe(0.7)Cr(1.3)O(3) was selected as the most promising material because of its response to C(2)H(4) and CO. Not only is the response to the individual analytes important, but the C(2)H(4) cross-sensitivity toward CO is also important. Fe(0.7)Cr(1.3)O(3) showed a good performance to C(2)H(4), with low cross-sensitivity to CO. In addition, when 0.16 ppm of phenanthrene is added, the sensor still has a slightly better response to C(2)H(4) than to CO. Nevertheless, the sensor exposure to high concentrations (>85 ppm) of polycyclic aromatic hydrocarbons led to signal saturation. On the other hand, the operation in wet conditions induces lower sensor sensitivity to C(2)H(4) and higher cross-sensitivity toward CO increase, i.e., the sensor response becomes similar for C(2)H(4) and CO.