A highly selective CO sensor using LaMnO3 electrode-attached zirconia galvanic cell

For enhancing the selectivity of a CO sensor, which comprises a zirconia galvanic cell and functions in accordance with a mixed electrode potential, perovskite-type oxides, LaMO3 (M = Mn, Cr, Fe and Co), have been found to be promising electrode materials. All these materials give higher sensitivity to CO than to H-2. The sensor attached with LaMnO3 electrodes exhibits a quick response (i.e., less than 10 s to reach 90% of the steady-state e.m.f. value) at 400 degrees C. Its e.m.f. to 2000 ppm CO is 6-18 times higher than that to the same concentration of H-2, CH4 or C3H8. Such high selectivity to CO seems to reflect that the catalytic activity of LaMnO3 is higher for the oxidation of CO than for that of H-2, CH4 or C3H8.