Additively manufactured mixed potential electrochemical sensors for NO_x, C₃H₈, and NH₃ detection

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. We find a correlation of increased sensitivity with larger gas reaction impedance, higher Pt electrode surface area, and slower diffusion.