Ppm level methane detection using micro-thermoelectric gas sensors with Pd/Al2O3 combustion catalyst films

The CH4 combustion performance of a micro-thermoelectric gas sensor (TGS) with Pd-Al2O3 catalysts prepared using two different methods, impregnation and colloid mixing, has been investigated. Three crystal phases of Al2O3, alpha, theta, and gamma, were used for the catalyst support; the Pd/theta-Al2O3 catalyst showed the best combustion performance. The Pd/O-Al2O3 catalyst exhibited the best dispersion of Pd nanoparticles as analyzed by both a pulse adsorption technique and transmission electron microscopy. The effect of the catalyst thickness on the H-2 and CH4 detection performance of the TGS using this Pd/theta-Al2O3 catalyst prepared using a colloid mixing method was investigated. It was found that the response voltage, Delta V, of the TGS to CH4 increased with increasing film thickness, but the Delta V to H-2 decreased. The TGS with the Pd/theta-Al2O3 catalyst whose thickness was 35 pin could detect as low as 1 ppm of CH4 in air by the thermoelectric conversion of the combustor heat to an electrical voltage. (C) 2014 Elsevier B.V. All rights reserved.