Highly selective sensor to CH/sub 4/ in presence of CO and ethanol using LaCoO/sub 3/ perovskite filter with Pt/SnO/sub 2/

In the present investigation, LaCoO/sub 3/ is used as an active filter for elimination of the sensor sensitivity to carbon monoxide and ethanol. A sol-gel procedure was used for the preparation of SnO/sub 2/ fine powder, which was impregnated with hexachloroplatinic acid to obtain 1.0 wt% Pt on SnO/sub 2/. The LaCoO/sub 3/ perovskite fine powder was prepared by citrate method, using nitrate precursors of La and Co, to act as active filter. The LaCoO/sub 3/ perovskite caused the sensitivity of the sensor to CO and ethanol declined significantly. It seems that the perovskite oxidizes CO and ethanol at temperatures lower than 250/spl deg/C whereas methane is not affected at temperature as high as 450/spl deg/C. This way the perovskite filter eliminates the sensor sensitivity to CO and ethanol, making the sensors highly selective to methane in presence of CO and ethanol in air.