CO2 detection with lithium solid electrolyte sensors

A CO2 sensor is set up by using an LiTi2(PO4)3+0.2Li3PO4 sintered material as a solid electrolyte and an Li2CO3+Li2O mixture as a detecting electrode. The measured electromotive force (e.m.f.) is in good accordance with the calculated e.m.f. for CO2 gas contents from 80 ppm to 1.3% at 650 °C. An NO2 gas presence of 100 ppm has little influence on the gas sensing. The e.m.f. value becomes lower than the calculated e.m.f. at an SO2 gas content of 20 ppm. The sensing ability is greatly interfered with by lithium sulfate formation on the detecting electrode surface. The sensor can detect CO2 concentrations between 1000 ppm and 1% at water vapour concentrations of 0-220 g/m3. The sensor can also operate well at CO2 gas concentrations from 100 ppm to 1% at 350 °C when an Li2CO3-K2CO3-Na2CO3 eutectic mixture is applied as the detecting electrode.