Detection of methane in oxygen-poor atmospheres using a catalytic asymmetric sensor design

A catalytic sensor for the detection of methane in oxygen-poor atmospheres has been tested. This sensor is based on the difference in catalytic activi ty of a ruthenium and a platinum electrode for the reaction of methane and CO2 to hydrogen. The electrolyte used is SrCe0.95Yb0.05O3-alpha (SCYb5), a high-temperature proton conductor. The sensor shows a good response to meth ane at 500 degreesC in a concentration range of 1-90 kPa with a small depen dence on the CO2 concentration, especially, at low methane partial pressure s (< 10 kPa). At temperatures higher than 500 degreesC, a maximum in the po tential difference of the sensor is detected. This maximum can be attribute d to a change in the electrode selectivity. It is shown that the sensor can be used to detect methane if the CO2 concentration is kept high enough, to ensure that there is no reaction change. The potential difference of the s ensor decreases with increasing temperature, which can be attributed to eit her the increasing electronic conductivity of the electrolyte, or a decreas ing catalytic activity difference between the electrodes. (C) 2001 Elsevier Science B.V. All rights reserved.