Electrochemical Gas Detection Based on Dynamic Measurements

Dynamic measurements are described for the solid state electrochemical detection of CO(2). The sensor device was built up in the same way as a type III potentiometric sensor based on the galvanic cell Pt/Na(x)CoO(2)/Na-beta/beta ''-Alumina/Na(2)CO(3)/Pt, CO(2), O(2). A periodically varying voltage was applied which results in a current changing with time as a result of the alternating cell reaction. The I/U characteristics of this process depends strongly on the specific dynamics of the sensor, i.e., the kinetics and thermodynamics of the cell reaction and also on the capacitive behaviour. In order to separate these different processes, measurements were carried out under various experimental conditions. The current-time dependence was investigated as a function of the CO(2) partial pressure, temperature and both amplitude and frequency of the applied voltage. It could be seen, that the effect of each process on the sensor performance is increased or decreased by the selection of appropriate sensor parameters. Kinetic, thermodynamic and capacitive responses are generally altogether involved in the sensor response.