Catalytic methane sensor using a Ni-CaZr0.9In0.1O3-alpha cermet electrode

A catalytic asymmetrical Nernst-type methane sensor with a porous Ni-CaZr0. 9In0.1O3-alpha, Cermet electrode has been developed. At 600 and 700 degrees C a Nernst-like behavior of the sensor is observed as a function of the met hane partial pressure with a slope of 56 and 26 mV/decade, respectively. At 500 degreesC a deviation from this behavior is found. The temperature depe ndence of the sensor response can be explained by the difference in catalyt ic activity of nickel and platinum. The sensor response depends on the CO2 concentration, but it is shown that the measured electromotive force can be corrected for the CO2 concentration in the gas mixture. The presence of wa ter in the gas mixture leads to a decrease of the sensitivity, which can be explained by the different catalytic response of nickel and platinum to th e presence of water. The sensor shows good reproducibility and long-term st ability. The effect of the gas flow rate on the sensor performance is found to be minimal. (C) 2000 The Electrochemical Society. S0013-4651(00)02-097- 8. All rights reserved.