| 摘要 |
PURPOSE:To decrease the influence of NOx and to improve the response characteristic of a gas sensor in place of an activated carbon filter by coating the surface of the sensor which utilizes the change in the resistance value of a metal oxide semiconductor with a reduction catalyst for NOx and removing the NOx by bringing the same into reaction with carbon monoxide. CONSTITUTION:The gas sensor 2 consists of a pair of electrodes 4, 6 in common use as heaters and the metal oxide semiconductor 8 consisting of SnO2, Fe2O3, In2O3, NiO, etc. The sensor detects carbon monoxide from the change in the resistance value of the semiconductor 8. A Pd catalyst for accelerating the responsiveness to carbon monoxide is added to the sensor by using, for example, SnO2. The reduction catalyst 10 for NOx is coated on the surface of the sensor 2. The NOx in a gas can thus be removed by bringing the same into reaction with carbon monoxide.
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