Calorimetric Thermoelectric Gas Sensor for the Detection of Hydrogen, Methane and Mixed Gases

A novel miniaturized calorimeter-type sensor device with a dual-catalyst structure was fabricated by integrating different catalysts on the hot (Pd/theta-Al2O3) and cold (Pt/alpha-Al2O3) ends of the device. The device comprises a calorimeter with a thermoelectric gas sensor (calorimetric-TGS), combining catalytic combustion and thermoelectric technologies. Its response for a model fuel gas of hydrogen and methane was investigated with various combustor catalyst compositions. The calorimetric-TGS devices detected H-2, CH4, and a mixture of the two with concentrations ranging between 200 and 2000 ppm at temperatures of 100-400 degrees C, in terms of the calorie content of the gases. It was necessary to reduce the much higher response voltage of the TGS to H-2 compared to CH4. We enhanced the H-2 combustion on the cold side so that the temperature differences and response voltages to H-2 were reduced. The device response to H-2 combustion was reduced by 50% by controlling the Pt concentration in the Pt/alpha-Al2O3 catalyst on the cold side to 3 wt%.