Electrochemical sensors based on proton-conducting electrolytes for determination of concentration and diffusion coefficient of CO2 in inert gases

The monitoring of CO2 levels in gases has important environmental, technological and energy applications. In the present work, results of the fabrication and testing of an amperometric-type sensor based on a proton-conducting material for analysing the concentration of carbon dioxide (CO2) in inert gases at elevated temperatures are presented. The analysis consists in reading the limiting current values determined during preliminary tests, obtaining the calibration dependence on variation of CO2 concentration and further using it for the investigation of gas mixtures. Experimental results show that the sensor is able to precisely detect CO2 concentration ranging between ~2 and 14 vol% in a wet N2 atmosphere at an intermediate-temperature range (500–600 °C) with a response time of ~30 min. Moreover, the possibility of estimating diffusion coefficients for CO2–N2 mixtures is also demonstrated. These results open a new window for high-temperature electrochemical analysis of gas mixtures, when solid-state gas sensors and proton-conducting electrolyte membranes are jointly utilised.