Calorimetric combustible gas sensor based on a planar thermopile array: fabrication, characterisation, and gas response

The development of a sensor for the detection of hydrogen and carbon monoxide in humid air is described. The device, which does not require external heating, utilises the heat of analyte combustion over a hydrophobic polymer-supported noble metal catalyst to generate a dc voltage from a planar tin dioxide thin film thermocouple array. Stable operation is demonstrated for the detection of analyte in the concentration range 20,000 ppm (2%) to 30 ppm in air. An analysis of the factors governing device sensitivity indicates that substrate thermal conductivity and catalyst batch activity have the most significant influence. Consideration of observed response data in the light of a simple theoretical model for predicting ideal sensor output indicates that this type of device operates most efficiently on exposure to low analyte concentrations, due to favourable heat transfer within the device under such conditions. (C) 2003 Elsevier B.V. All rights reserved.