Selective CO gas detection of CuO- and ZnO-doped SnO2 gas sensor

CuO (1–10 mol%) and ZnO (3 mol%) were independently or simultaneously added to SnO2 to change the selectivity between CO and H2 gases of pellet-type SnO2 sensor. The effects of the additives on the electrical conductivity and thus the sensitivity to 200 ppm CO and 200 ppm H2 gases were examined in the temperature range from 80 to 450°C. The electrical conductivity of SnO2 was drastically decreased by the addition of either CuO or ZnO. CuO addition to SnO2 lowered the temperature showing the maximum sensitivity value for either CO or H2 gases. On the other hand, ZnO addition made SnO2 to be more sensitive to H2 gas at higher temperatures. Consequently, SnO2 sensor co-doped with ZnO and CuO showed a high selectivity to CO gas (SCO/SH2∼5) at ∼160°C.