Selective CO gas detection of SnO2–Zn2SnO4 composite gas sensor

For the selective detection of CO against H2 gas, SnO2–Zn2SnO4 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 H2) were examined by measuring the current–voltage (I–V) characteristics of the composite sensors between 80 and 450°C. ating of CuO lowered the temperature showing the maximum sensitivity of SnO2 for either CO or H2 gas. However, the addition of small amount of spinel zinc stannate (Zn2SnO4) into SnO2 provided the sensitivity to CO gas at low temperature (∼270°C) while the sensitivity to H2 gas was maintained at high temperature (∼340°C). Further increase of Zn2SnO4 content moved the sensitivity curves to CO and H2 gases toward high temperature. Thus, the high selectivity for CO gas was obtained in the temperature range between 150 and 300°C depending upon Zn2SnO4 content.