NON-NERNSTIAN POTENTIOMETRIC ZIRCONIA SENSORS - SCREENING OF POTENTIAL WORKING ELECTRODE MATERIALS

Fully-stabilized zirconia solid electrolyte cells were made with a Pt reference electrode and working electrodes consisting either of Mo or of binary alloys of Pt with one of the elements Ag, Au, Ni, Cu, Rh. Th e e.m.f. of the cells was measured in the flue gas of a natural ps bur ner in the presence of oxidizable gases like CO and H-2. The values ar e higher than predicted by the Nernst equation, depending on the amoun t of CO and H-2 present in the flue gas (so-called non-Nernstian elect rode potential, NNEP). The H-2 sensitivity exceeds the CO sensitivity; the ratio of both depending on the electrode material used. The Pt/Au electrode was found to exhibit an excellent long-term stability where as a strong degradation of the NNEP was observed at electrodes made of the other materials.