Extension of proton conductor sensors

Most proton conductor sensors have aimed at sensing of Hj in inert gases or air, as mentioned above. However, other chemical components are also sensitive whenever they produce or consume protons through electrode reactions. Typical of such examples are and 

In the cases of CO and NH3, the following electrode reactions are involved, respectively, and compete with the proton-consuming reaction (36.6). 

In the presence of water vapour, CO can be sensitive with devices usually having Pt electrodes. However, the sensitivity (short-circuit current) is about one tenth of that of H2 at the same concentration . The choice of other electrodes may be varied to increase CO sensitivity. For example, the use of a pair of oxide electrodes, Pt-loaded WO3 and Pt-loaded Sn02, in an amperometric element has been shown to increase CO sensitivity to about seven times as high as the H2 sensitivity.  

For sensing of NH3, Pt electrodes show sufficiently high sensitivity. The four-probe type element (Fig. 36.4) can reportedly detect 50-5000 p.p.m. NH3 in air at room temperature F 

Schnell, G. Velasco and Ph. Colomban, Solid State Ionics 5 (1981) 291-4. 

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