Working mechanism of an ethanol filter for selective high-temperature methane gas sensors

Semiconducting metal-oxide gas sensors are generally nonselective, which limits their use as natural gas detectors in domestic environments when ethanol is present in high background concentrations. Using a thin-film Ga/sub 2/O/sub 3/ sensor with a thick-film catalyst filter of Ga/sub 2/O/sub 3/ and an operating temperature of 800/spl deg/C, the cross-sensitivity to ethanol is strongly reduced and the sensor response to methane is enhanced. Detection of natural gas is made reliable and the rate of false alarms is reduced. Oxidation of ethanol and methane over gallium oxide is studied using GC product analysis. These measurements of catalytic activity help to clarify the reactions involved in the filtering mechanism. Elimination of the ethanol cross-sensitivity is attributed to the thermal combustion of ethanol as it passes over the hot filter. The sensor response to methane is enhanced as methane is activated by the active catalytic Ga/sub 2/O/sub 3/ thick-film.