Humidity effects on the initial stabilization behavior of a solid electrochemical CO2 sensor

Abstract

An electrochemical-type CO2 sensor using alkali carbonate as a sensing material was studied, along with its humidity disturbance effect during the initial stabilization stage. A sensor made of Na2CO3 (Cell A) and NaHCO3 (Cell B) sensing materials were tested from room temperature to 500 degrees C, step-by-step, at CO2 concentration of 500 ppm. The test was designed to investigate the difference in the initial stabilizing step between dry and humid conditions. After measuring the sensitivity of both Cell A and B, the NaHCO3 sensing material showed a sensitivity value similar to that of the Na2CO3 sensing material during operation at 500 degrees C. The thermodynamic calculation implied that the NaHCO3 that might be produced in humid air was considered the main source of sluggish behavior due to the decomposition of NaHCO3 to Na2CO3 at 250 degrees C. In addition, the electric potential calculation based on the chemical reaction of Cell A and Cell B was performed to compare the simulated model with the real behavior of the sensor.