Combined amperometric-potentiometric oxygen sensor

Abstract

The present investigation describes the results of the performance and the assessment of a combined electrochemical oxygen sensor, equipped with a diffusion barrier and consisted of an electrochemical cell-pump and a potentiometric cell. Both cells of the oxygen sensor are based on the same solid electrolyte, having 0.91ZrO2 + 0.09 Y2O3 composition. More precisely, the sensor consists of: i) an electrochemical cell served for electrochemically pumping-out of oxygen from the sensor chamber, operating as an amperometric sensor and ii) a second electrochemical cell served for measuring the oxygen content in the sensor chamber and operating in potentiometric mode. The analyzed gas is used as the test gas for the second cell, operating under potentiometric regime. The second cell allows studying the sensor's internal oxygen content as well. The presence of the potentiometric cell increases the reliability of the sensor due to simultaneous measurement of the values of the limiting current in the cell-pump and of the electromotive force in the potentiometric cell. The as fabricated sensor is found to be very effective, providing rapid and accurate response for gas mixtures containing within the range of minimal to nearly 90% (0,8–88%) oxygen concentrations at operating temperature values between 400–700 °C. The sensor response time at 500 °C does not exceed the 60 s. The sensor allows measuring the oxygen diffusion coefficient in nitrogen in a wide range of high temperature values as well. © 2020 Elsevier B.V.