Simultaneous response of work function and resistivity of some SnO 2-based samples to H 2 and H 2S

Abstract

The simultaneous response of the work function and resistivity to H 2 and H 2S of some pure and doped SnO 2 samples in the form of thick films is measured in humid laboratory air. The gas-sensitive layer of thick-film samples is screen printed on alumina substrates containing gold electrodes on a finger-like structure. Palladium and silver are used as catalytic activators in the SnO 2. The work function change is measured with a vibrating capacitor (Kelvin probe) automatically compensated by a feedback system and with graphite as the reference electrode. Silver doping has a large effect on the response to H 2S at temperatures around 150°C, but no effect is found in the case of exposure to H 2 at these temperatures. Palladium doping has an effect only in the case of H 2 exposure, the effect being strongest at lower temperatures around 150°C. The resistance changes give much higher values for the calculated work function changes as compared to the measured ones in the case of H 2S exposure at 420 and 620 K, whereas in the case of H 2 exposure, the measured one are higher and a linear dependence between the calculated and measured changes of work function is obtained.