Amperometric NO sub(x) Sensor Based on Oxygen Reduction

• Published in: IEEE sensors journal Vol. 16; no. 6; pp. 1532 - 1540
• Main Authors: Soykal, IIlgaz, Matter, Paul H, Thrun, Lora B, Long, Richard Q, Swartz, Scott L, Ozkan, Umit S
• Format: Journal Article
• Language: English
• Published: 01.03.2016
• Subjects: Combustion; Electrical measurements; Exhaust; Nitrogen oxides; Oxygen; Partial pressure; Reduction (electrolytic); Sensors
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2015.2498544

A novel ceria-based amperometric NO sub(x) and NH sub(3) sensor was investigated. The sensor consisted of gadolinium-doped ceria electrolyte membrane with (La sub(0.60)Sr sub(0.40)) (Co sub(0.20)Fe sub(0.80)) $\text{O}_{3-\delta }$ (LSCF) electrodes applied to opposite sides. The assembly operated in combustion exhaust streams with higher sensitivity to both NO sub(x) and NH sub(3), less dependence on oxygen partial pressure, and faster response than previously reported. The sensor had an operational temperature range of 200 degree C-550 degree C and was resistant to common exhaust gas contaminants, such as steam, CO sub(2), and sulfur oxides. Electrochemical testing and in-situ DRIFTS studies showed NO sub(x) adsorption on the sensor causing accelerated kinetics for oxygen reduction reaction (ORR) whereby adsorbed NO sub(x) species acted as a catalyst for an alternative ORR pathway, thus enabling an amperometric sensing mechanism.