Gas Polarographic Oxygen Sensor Using an Oxygen/Zirconia Electrolyte

Abstract

A new type of oxygen sensor using the electrochemical oxygen pump of a zirconia electrolyte and the artificial oxygen diffusion overpotential behavior has been investigated from the theoretical and practical viewpoints of the "gas polarography," the concept of which is proposed in this paper. This new oxygen sensor has excellent oxygen sensing characteristics analogous to polarography. As a result of the artificial oxygen diffusion overpotential at the cathode, the reproducible limiting current relating to the oxygen concentration was observed over a wide oxygen concentration range up to 95% and a temperature range of 400°–700°C in gas mixtures. In this paper, the factors influencing the limiting current in the normal diffusion region, that is, the oxygen molar fraction, gaseous diffusion coefficients, the temperature, the pressure, and the two geometric quantities (area and length) of the gas diffusion hole are theoretically considered.