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. The e.m.f. of the cells was measured in the flue gas of a natural ps burner in the presence of oxidizable gases like CO and H-2. The values are higher than predicted by the Nernst equation, depending on the amount of CO and H-2 present in the flue gas (so-called non-Nernstian electrode 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 whereas a strong degradation of the NNEP was observed at electrodes made of the other materials.