Selective CO gas detection of SnO 2–Zn 2SnO 4 composite gas sensor

Abstract

For the selective detection of CO against H 2 gas, SnO 2–Zn 2SnO 4 composite-type sensors were fabricated. The surface of the pellet-type composite sensors was coated by CuO after sintering at 1000°C for 3 h. The electrical conductivity and the sensitivity of the sensors to reducing gases (200 ppm CO and 200 ppm H 2) were examined by measuring the current–voltage ( I– V) characteristics of the composite sensors between 80 and 450°C. The coating of CuO lowered the temperature showing the maximum sensitivity of SnO 2 for either CO or H 2 gas. However, the addition of small amount of spinel zinc stannate (Zn 2SnO 4) into SnO 2 provided the sensitivity to CO gas at low temperature (∼270°C) while the sensitivity to H 2 gas was maintained at high temperature (∼340°C). Further increase of Zn 2SnO 4 content moved the sensitivity curves to CO and H 2 gases toward high temperature. Thus, the high selectivity for CO gas was obtained in the temperature range between 150 and 300°C depending upon Zn 2SnO 4 content.