CO gas sensor based on Au–La2O3 added SnO2 ceramics with siliceous zeolite coat

Abstract The CO selective gas sensor based on La 2 O 3 –Au/SnO 2 ceramics had a high selectivity to CO among H 2 , CH 4 , i-C 4 H 10 and C 2 H 4 ; while a high sensitivity to C 2 H 5 OH. An acidic catalyst layer converting C 2 H 5 OH into C 2 H 4 with a low sensitivity by dehydration was coated on the sensing layer of the La 2 O 3 –Au/SnO 2 ceramics to reduce the sensitivity to C 2 H 5 OH. Ferrierite, one of siliceous zeolites, was found to have a prominent ethanol filtering effect; such a prominent performance was related to a strong acid strength and a large acid amount. The siliceous zeolites have a hydrophobic property, a specific area of more than a few hundreds in m 2 g −1 and a thermal stability. As for the ethanol filtering effects, k a / D ≥10 5 was estimated on the basis of a simple model of chemical dynamics, k : a rate constant of dehydration, a : an effective reaction area of the catalyst layer, D : a diffusion coefficient in the filtering layer of ferrierite. As a result, a CO selective gas sensor with a sensitivity to CO over ten times higher than that to the other gases was obtained at about 300°C.