Highly selective sensor to CH4 in presence of CO and ethanol using LaCoO3 perovskite filter with Pt/SnO2

In the present investigation, LaCoO₃ 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 SnO₂ fine powder, which was impregnated with hexachloroplatinic acid to obtain 1.0 wt% Pt on SnO₂. The LaCoO₃ perovskite fine powder was prepared by citrate method, using nitrate precursors of La and Co, to act as active filter. The LaCoO₃ 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°C whereas methane is not affected at temperature as high as 450°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.