Development of a NO_x and NH₃ sensor for automotive exhaust applications and control of industrial process

Gita Nematbakhsh Abkenar (1, 2, 3) , Mathilde Rieu (1, 2, 3) , Philippe Breuil (1, 2, 3) , Jean-Paul Viricelle (1, 2, 3)

1 LGF-ENSMSE - Laboratoire Georges Friedel
2 SPIN-ENSMSE - Centre Sciences des Processus Industriels et Naturels
3 PTSI-ENSMSE - Département Procédés de Transformations des Solides et Instrumentation

According to new European driving cycle, while the vehicular emissions of NO_x and CO have decreased over the past years, ammonia emissions have considerably increased. Among all NO_x reduction approaches that have been developed, selective catalyst reduction (SCR) system using ammonia as a reductant is one the most reliable ways to control the NO_x emissions from diesel engine vehicles and trucks. In order to optimize the conversion rates of NO_x and to prevent inducing excessive NH₃ to the air, an NH₃ and NO_x sensor is required to control the SCR system. Ivan Romanytsia et al. in 2015 have developed three-electrode mixed-potential selective NO₂ sensors. Based on this study, we aim to develop sensors for selective detection of both NO_x and NH₃ for the exhaust of automotive. In this work, mixed potential gas sensors are fabricated by using two sensing materials of Au and Au-V₂O₅ as working electrodes, YSZ as electrolyte and platinum as reference and counter electrode. In order to evaluate the performance of the fabricated planar sensors, the response to different pollutant gases such as CO, NH₃, NO₂ and NO in respective amounts of 100, 20, 100 and 100 ppm are studied in a base gas composed of 12% O₂ and 1.5% H₂O, balanced with N₂. The sensor signal (ΔV_ref) is the difference of potential between the reference (Pt) and the working electrode. In order to take into account irreproducibility of the sensors due to fabrication process, all tests are reproduced with two sensors (A and B). Since NO₂ is an oxidizing gas, the galvanostatic mode can only produce the electro-chemical reduction of NO₂ at working electrode. Figure 1a shows the variations of the potential at 450 °C for different gases by applying a polarization current of 25nA from working to counter electrode. In these conditions, the responses to other interfering gases such as CO and NH₃ are removed while there is relatively a good selectivity towards NO₂. Concerning ammonia gas sensors, Au-V₂O₅ working electrodes displayed a high sensitivity to NH₃ as well as fast response and recovery times at 600 °C (figure 1b). In order to achieve an integrated NO_x and ammonia sensor, which works simultaneously at the same temperature, further investigations are needed.

Mots clés: Mixed potential sensor; Ammonia sensor; NOx sensor; Selectivity; Polarization; Exhaust gas

Domaines: Génie des procédés

Gita Nematbakhsh Abkenar, Mathilde Rieu, Philippe Breuil, Jean-Paul Viricelle. Development of a NO_x and NH₃ sensor for automotive exhaust applications and control of industrial process. Journée Scientifique 2018 du Codegepra, Nov 2018, Saint-Etienne, France. , Journée scientifique du CODEGEPRA - Le Génie des Procédés en Rhône-Alpes Auvergne, pp.P4. ⟨hal-01973343⟩