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

Abstract The CH 4 combustion performance of a micro-thermoelectric gas sensor (TGS) with Pd–Al 2 O 3 catalysts prepared using two different methods, impregnation and colloid mixing, has been investigated. Three crystal phases of Al 2 O 3 , α, θ, and γ, were used for the catalyst support; the Pd/θ-Al 2 O 3 catalyst showed the best combustion performance. The Pd/θ-Al 2 O 3 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 CH 4 detection performance of the TGS using this Pd/θ-Al 2 O 3 catalyst prepared using a colloid mixing method was investigated. It was found that the response voltage, Δ V , of the TGS to CH 4 increased with increasing film thickness, but the Δ V to H 2 decreased. The TGS with the Pd/θ-Al 2 O 3 catalyst whose thickness was 35 μm could detect as low as 1 ppm of CH 4 in air by the thermoelectric conversion of the combustor heat to an electrical voltage.