Amperometric NOx Sensor Based on Oxygen Reduction

A novel ceria-based amperometric NOx and NH3 sensor was investigated. The sensor consisted of gadolinium-doped ceria electrolyte membrane with (La0.60Sr0.40) (Co0.20Fe0.80)O3-delta (LSCF) electrodes applied to opposite sides. The assembly operated in combustion exhaust streams with higher sensitivity to both NOx and NH3, less dependence on oxygen partial pressure, and faster response than previously reported. The sensor had an operational temperature range of 200 degrees C-550 degrees C and was resistant to common exhaust gas contaminants, such as steam, CO2, and sulfur oxides. Electrochemical testing and in-situ DRIFTS studies showed NOx adsorption on the sensor causing accelerated kinetics for oxygen reduction reaction (ORR) whereby adsorbed NOx species acted as a catalyst for an alternative ORR pathway, thus enabling an amperometric sensing mechanism.