Abstract
Solid oxide fuel cells (SOFCs) using Pd metal as the anode were fabricated for detection of CO in a flowing mixture of 0–4000 ppm CO, 50% H 2, 10% CO 2 and 6% H 2O vapor between 300 and 400 °C. When 20 mol% Sm 3+-doped CeO 2 (SDC) was used as the electrolyte, the Pd anode was subjected to a large and reversible change in the anodic-reaction resistance with the CO concentration. This behavior brought about an almost linear relationship between the electromotive force (EMF) generated from the cell or the short-circuit current through the cell and the logarithm of the CO concentration. In both signals, the minimum detectable CO concentration was 50 ppm, and the 90% response and 90% recovery times were about 60 s. However, the EMF of the cell at a CO concentration of 0 ppm significantly deviated from the theoretical value, which made it difficult to obtain reproducible data. In addition, the current signal of a few μA at a CO concentration of 4000 ppm was not large enough to monitor the CO concentration exactly. The improvement of these problems could be achieved by using 25 mol% Y 3+-doped BaCeO 3 (BCY25) with higher ionic conduction as the electrolyte: the EMF of the cell at a CO concentration of 0 ppm was near the theoretical value; the current signal reached 66 μA at a CO concentration of 4000 ppm.
Published Version
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