THEORY OF GAS SENSORS - RESPONSE OF AN ELECTROCHEMICAL SENSOR TO MULTICOMPONENT GAS-MIXTURES

A first-principles model of the operation of an electrochemical metal oxide gas sensor had been previously used to analyze the response when the sensor was exposed to a simple gas mixture (e.g. O-2/CO/CO2). Her e, the model is extended to study the sensor response to a complex gas mixture containing two reducing gases e.g, O-2/CO/CO2/H-2/H2O. In a f irst version, it is assumed that there is no interaction between the r educing and product gases (e.g. CO and H2O or H-2 and CO2). The respon se to the complex gas mixture is deduced using the values of the model parameters obtained by fitting the experimental results for the simpl e gas mixtures O-2/CO/CO2 and O-2/H-2/H2O individually. In the second version, the so-called 'water gas' reaction between adsorbed species i s included. A wide variety of response is predicted depending upon the electrode material, the reactivities of the gases and the rate of rea ctions involving product gases. This analysis is helpful in providing insight and design guidance in optimizing sensor operation for specifi c applications.