Electrode air-reference

The electrodes and electrode protective coating of the oxygen sensor play a crucial role in determining the performance characteristics and durability (2). The electrodes used are the inner or air-reference electrode and the outer or exhaust gas electrode. The protective coating goes over the outer or exhaust electrode. While a complete discussion of the requirements and properties of the electrodes and electrode protective coating is beyond the scope of this paper, a brief description will be given. 

Gas sensors — (b) Gas sensors with solid electrolytes — Figure 4. Voltage characteristics of an idealized hydrocarbon electrode vs. Pt-air reference electrode in propylene-containing mixtures... 

Another alternative, an ionized air reference electrode (IAE), has been described by Foulkes et al. [66] for use with solid polymer electrolytes, in particular Nafion 425. Use of the IAE is achieved by establishing electrical contact with the solid electrolyte from a weak source of ionizing radiation to ionize an air gap. In contrast to conventional reference electrodes, the IAE is a liquid-free device and can make electrical contact with a solid polymer electrolyte without a salt bridge. It is also temperature independent. In view of these special characteristics, the IAE might provide a useful alternative to conventional reference electrodes for use with solid polymer electrolytes. 

From the data [57] concerning determination of the emf of the dissociated electrolyte in relation to the air reference electrode, it can be found that for the electrons localized on the anion vacancies in electrolyte (Zr02)o.9(Y203)o.i, the polar correction is equal to 0.4 eV. 

For a potentiometric oxygen sensor with an air reference electrode and the sensor signal... 

Heat conducting box Measuring electrode Solid electrolyte disc Air reference electrode Thermocouple Electric heater Heat isolation... 

Figure 25-34. Comparison of the plots of the signal from a galvanic solid-electrolyte probe with an air reference electrode and the signal of an infrared device for CO measurements versus time during the reducing phase of burning porcelain [52].

Fig. 10 a Charge nx>files for the Li/PEOigLiTFSI-2G4/LATP/saturated LiCl aqueous solution/Pt, air cell at 1 mA cm and 60 °C, and b impedance profiles after each polarization period. The cell voltage and impedance were measured using a platinized platinum air reference electrode (from Ref. [61])... 

Fig. 1. Schematic drawing of oxygen sensors (a) conventional type (air reference electrode), (b) minisensor with Pd-PdO reference system, (c) sensor with zirconia tip measuring electrode, [Fouletier, 1982/83].

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