Effect of macrostructural control of an auxiliary layer on the CO 2 sensing properties of NASICON-based gas sensors

Abstract

Macrostructural effects of an auxiliary electrode on the CO 2 gas sensing properties of NASICON (Na 3Zr 2Si 2PO 12) solid-electrolyte sensors were investigated. The sensor with a porous Li 2CO 3–BaCO 3-based auxiliary layer (mp-Sensor), which was prepared by utilizing constituent metal acetates and polymethylmethacrylate microspheres as a template, showed faster CO 2 response and recovery and smaller cross-response against humidity changes than those obtained with a dense auxiliary layer without pores (d-Sensor). The magnitude of CO 2 response of mp-Sensor was slightly larger than the theoretical one, probably due to the existence of impurities which might have reacted with CO 2 in the auxiliary layer. On the other hand, c-Sensor with a thicker and dense auxiliary layer, which was prepared by commercially available carbonates, showed smaller CO 2 response and larger cross-response to humidity than mp-Sensor and d-Sensor. Thus, the use of the porous auxiliary layer prepared by constituent metal acetates was confirmed to be effective for improving the CO 2 sensing properties along with the large CO 2 response and small cross-response to humidity.