Solid electrolyte gas sensors based on mixed potential principle – A review

The development of kinetically controlled potentiometric solid electrolyte gas sensors, called shortly mixed potential sensors (MPS) started with the discovery of kinetic limitations of equilibrium establishment on poisoned oxygen sensors based on yttria stabilized zirconia (YSZ) equipped with platinum electrodes. The decades of development of these sensors generated a broad knowledge on the signal establishing and influencing processes at the interface between gas, electrode and electrolyte as well as on a variety of possible materials for improved sensitivity, selectivity and long-term stability. Furthermore, this knowledge was extended by approaches directed on electrochemical dynamic conditioning of such sensors and the coupling with other physical quantities like temperature and light. The broad knowledge enabled an extended field of applications in automotive, food, medical, electric and chemical industries. The variety of analytes to be addressed by these sensors beside the most prominent ones like CO, hydrocarbons (HC), NOx, NH3 and H2 is constantly increasing. The present review gives an overview on the historical development, the basics of theory of operation, the analytes and materials as well as applications. Regarding the publications, the work continues the overview given in former review articles.