Solid-state potentiometric CO2 sensor combining Li3PO4 with MoO3-doped Li2CO3 sensing electrode

The potentiometric CO2 gas sensors based on Li3PO4 thin film using different MoO3-doped Li2CO3 as sensing electrodes were investigated. The sensing electrode materials were prepared by screen printing while the Li3PO4 electrolyte thin film by thermal evaporation. The materials’ phase composition and the microstructures were characterized by X-ray diffraction (XRD), energy-dispersive spectrum (EDS), and scanning electron microscopy (SEM). The sensors were tested at the temperature ranging from 350 °C to 500 °C with an interval of 25 °C. The results showed that all sensors have better sensing properties at higher working temperatures. Among them, the sensor attached with 10 wt% MoO3-doped Li2CO3 exhibit excellent sensing performance, and its sensitivity attains to 95.7 mV/decade and the response and recovery time are 16 s and 22 s respectively at 500 °C. Its output EMF is more stable than any other sensors annealed at 550 °C. The MoO3-doped Li2CO3 sensing electrodes can significantly improve the sensors’ properties because of the porous microstructure and catalytic characteristics during the reaction period.