Publications

Abstract not provided.

Sensors to detect mixtures of NO_x/NH₃ are needed to monitor emissions of diesel automobiles where a selective catalytic reduction system uses an NH₃ mediated reaction to reduce NO_x. We report on the application of a three electrode La_0.8Sr_0.2CrO₃, Au_0.5Pd_0.5, Pt mixed potential sensor using yttria-stabilized-zirconia (YSZ) as a solid electrolyte to NO_x/NH₃ sensing. Artificial neural networks were used to automatically decode the concentrations of NO_x/NH₃ and errors of less than 15% are achieved. The optimal architecture for ANN decoding and the maximum density of training data points are also determined. The stability of the sensor was monitored by electrochemical impedance spectroscopy. The impedance associated with YSZ oxygen ion conduction and the electrochemical reactions at the three-phase interface are tracked for a period of over 100 days.

Additive manufacturing of mixed potential electrochemical sensors opens the possibility to perform rapid prototyping of electrode and electrolyte materials. We report for the first time the use of this technique for the fabrication of solid-state electrochemical gas sensors of the mixed potential type and assessment of variability in the manufacturing process. La_0.87Sr_0.13CrO₃ (LSCO) and Pt electrodes bridged with a porous yttria-stabilized zirconia (YSZ) have been deposited on YSZ substrates by direct-write extrusion of pastes and inks. The sensors are evaluated for their sensitivity to 200 ppm of NO_x, C₃H₈, and NH₃. There is a need to understand how variations in intrinsic materials parameters during manufacturing such as differences in porosity affect the gas sensing of additively manufactured sensors to guide optimization of their performance and serve as quality control techniques. Further characterizations of these devices include electrochemical impedance spectroscopy and an aqueous electrochemical assessment of the electrode surface area and diffusion through the porous layer. In conclusion, we find a correlation of increased sensitivity with larger gas reaction impedance, higher Pt electrode surface area, and slower diffusion.