Novel Solid Electrolyte CO₂ Gas Sensors Based on c‑Axis-Oriented Y‑Doped La_9.66Si_5.3B_0.7O_26.14

Nowadays, monitoring and recording CO₂ gas has become more and more important in various areas, leading to increasing demand for developing high-sensitive CO₂ sensors. In this study, a novel potentiometric CO₂ gas sensor is designed based on a new solid electrolyte of Y-doped La_9.66Si_5.3B_0.7O_26.14 (Y-LSBO), coated with the Li₂CeO₃–Au–Li₂CO₃ composite as a sensing electrode and Pt as a reference electrode. With the optimized composition of a sensing electrode, the electromotive force (EMF) varies linearly with the logarithm of the CO₂ concentration in the range of 400–4000 ppm, exhibiting an excellent Nernstian response to CO₂ gas in both dry and humid atmospheres. The fabricated CO₂ sensor can be well operated at 400 °C in a dry atmosphere and 450 °C in a humid atmosphere. Based on the results, we have proposed that the good CO₂ sensing performance may be associated with Li₂CeO₃ playing a role of “ionic bridge” between the O^2– conductor (Y-LSBO) and the Li⁺ conductor (Li₂CO₃). This study not only shows the promising potential of a Y-LSBO solid electrolyte utilized in the field of gas sensors but also enriches the research of solid electrolyte–based potentiometric CO₂ gas sensors.