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

The development of a solid state potentiometric sensor able to work up to 3 00 degreesC is described. In this sensor, a very thin membrane of alpha -zi rconium acid phosphate, obtained by colloidal dispersion of exfoliated alph a -Zr(HPO4)(2) and acting as a proton conductor, is interposed between a ca talytic electrode (platinum) and a solid state reference electrode (a silve r disk anodically coated with Ag2O). Both the proton conductor and the refe rence electrode were thermally stable at the above temperature. The sensing electrode became more and more active with the increasing temperature, all owing the detection even of some species towards which the sensor is inert at lower temperature. Preliminary investigations showed that its emf depend s on the partial pressure of oxygen. When used in air at 200-300 degreesC, the sensor can detect oxidable gaseous species such as hydrocarbons and alc ohols. The sensitivity obtained is of the order of a few ppm. Some consider ations on the detection mechanism, as well as on the potentiality of this s ensor for its use in the detection of oxidable polluting agents in air are also reported. (C) 2001 Elsevier Science B.V. All rights reserved.