Solid state potentiometric sensor at medium temperatures (150–300°C) for detecting oxidable gaseous species in air

The development of a solid state potentiometric sensor able to work up to 300°C is described. In this sensor, a very thin membrane of α-zirconium acid phosphate, obtained by colloidal dispersion of exfoliated α-Zr(HPO4)2 and acting as a proton conductor, is interposed between a catalytic electrode (platinum) and a solid state reference electrode (a silver disk anodically coated with Ag2O). Both the proton conductor and the reference electrode were thermally stable at the above temperature. The sensing electrode became more and more active with the increasing temperature, allowing the detection even of some species towards which the sensor is inert at lower temperature. Preliminary investigations showed that its emf depends on the partial pressure of oxygen. When used in air at 200–300°C, the sensor can detect oxidable gaseous species such as hydrocarbons and alcohols. The sensitivity obtained is of the order of a few ppm. onsiderations on the detection mechanism, as well as on the potentiality of this sensor for its use in the detection of oxidable polluting agents in air are also reported.