Nano-structured thin-film Pt catalyst for thermoelectric hydrogen gas sensor

A hydrogen gas sensor using thermoelectric thin-film of nickel oxide with platinum catalyst thin-film on half of its surface Pt/NiO/alumina was fabricated and showed prominent selectivity for hydrogen gas. The platinum catalyst thin-film plays the most important role for its detection mechanism and its catalytic activity which depends both on surface morphology and thickness was investigated using Pt/Si. The surface morphology of platinum film deposited on Si by sputtering with low r.f. power showed that the small grains with the diameter around 20 nm agglomerated. The catalytic activities of the Pt films were increased with the film thickness and saturated above a thickness of 60 nm. By increasing the r.f. power, Pt films of the larger grains with the diameter around 40 nm were obtained and their catalytic activities were less than those of smaller grains. However, the catalytic performance of the Pt film with the thickness over 150 nm was unaffected by the grain size. In order to investigate the temperature dependence of the catalytic activity and the properties of the Pt/NiO/alumina sensor, a non-contacting in situ monitoring experimental-set equipped with an infra-red camera was employed in this study. (C) 2003 Elsevier Science B.V. All rights reserved.