A first principles model of metal oxide gas sensors for measuring combustibles

A first principles model is described for the operation of electrochemical type sensors designed to measure combustibles in air. It is based on the general principles presented in previous publications (A.D. Brailsford, E.M. Logothetis, Sens. Actuators, 7 (1985) 39-67; A.D. Brailsford, M. Yussouff, E.M. Logothetis, Sens. Actuators, B 13 (1993) 135-138; A.D. Brailsford, RI. Yussouff, E.M. Logothetis, M. Shane, Sens. Actuators, B 24-25 (1995) 362-365; A.D. Brailsford, M. Yussouff, E.M. Logothetis, Sens. Actuators B 34 (1996) 407-411; and A.D. Brailsford, M. Yussouff, E.M. Logothetis, Sens. Actuators, B 35-36 (1996) 392-397) for an ab initio model developed to describe the operation of metal oxide oxygen sensors. The authors show that the e.m.f. of the combustibles sensor may be written as the difference between the e.m.f.s of two non-identical air-referenced oxygen sensors. This helps in the qualitative understanding of the observed and predicted responses of the combustibles sensors. The present model is used to analyze experimental data reported in the literature (H. Okamoto, H. Obayashi, T. Kudo, Solid State Ion. I (1980) 319-326; and A. Vogel, G. Baler, V. Schuele, Sens. Actuators B 15 (1993) 147-150) and to indicate the variety of behavior expected from these sensors depending on the properties of the electrode materials. This analysis is expected to aid the design and optimization of these sensors. (C) 1998 Published by Elsevier Science S.A. All rights reserved.