Suppression of NO and SO2 cross-sensitivity in electrochemical CO2 sensors with filter layers

Interfering effects of NO and SO2 gases on CO2 sensing performance of the solid state galvanic cell, Pt, O2, CO2, Na2CO3–BaCO3ǀǀNa+ǀǀNa2Ti6O13–TiO2, O2, Pt were investigated at 673 K and 773 K. In the interfering gases concentration ranges of 50–150 ppm NO and 5–15 ppm SO2, exposure to NO gas guaranteed a recovery of electromotive force (EMF) from the relatively small EMF deviation. However, SO2 gas remarkably degraded the performance of the sensor arising from the formation of sulfate on the sensing electrode. Na2CO3–SnO2, Na2CO3–SnO2–Cu, and Na2CO3–SnO2–CuO were heat-treated and adopted as filter materials adjacent to the sensing electrode. The EMF response of the CO2 sensors with filters was compared in terms of filter efficiency. Among them, Na2CO3–SnO2–CuO filter showed the most promising characteristics in suppressing NO and SO2 gas interference.