The CO and H2 gas selectivity of CuO-doped SnO2-ZnO composite gas sensor

For the selective detection of reducing gases (CO gas against H, gas, or vice versa), SnO2-ZnO composites were fabricated and the surface was coated with CuO. The electrical conductivity and the CO and the H-2 gas sensing properties of CuO-coated SnC2-ZnO composites were examined between 80 and 450 degreesC. The CuO, coated and thus doped to SnO2, apparently acted as a catalyst and thus lowered the sensing temperature and slightly increased the sensitivity values for both CO and H-2 gases. The ZnO addition into CuO-cloped SnO2 increased the sensitivity to CO gas at low temperature and the sensitivity to H, gas at high temperature due to the combined effect of the microstructure and the composition. As a result, the high selectivity for CO gas was obtained between 150 and 250 T while the high selectivity for H, gas was shown bctween 310 and 400 degreesC, depending upon the ZnO content. As the content of ZnO increases above 3 mol%, both the CO and the H-2 selectivities decreased. (C) 2002 Elsevier Science B.V. All rights reserved.