Bismuth Oxide-Based Semiconductor Gas Sensor for Nitrogen Monoxide

Abstract

A search for semiconducting oxides was carried out to design a sensor selective to NO over NO₂. Bi₂0₃ was very selective to NO though not very sensitive among the various oxides examined, and NiO was proved to be the most effective promoter to Bi₂0₃ for enhancing NO sensitivity. The sensor element using 5wt%NiO-Bi₂O₃ showed fairly good sensing properties to NO in the range of 0-400ppm in sensitivity, selectivity over NO₂ and response rate, at 300°C. The cross-sensitivities to C₃H₆, C₃H₈, H₂ and O₂ were modest or insignificant, compared to the sensitivity to NO. Catalytic activity tests and TPD measurements indicated that the response to NO (increase in resistance) was associated with its reaction with the surface oxygen of the element, while that to NO₂ (decrease in resistance) resulted from its anionic adsorption.