Influence of Reduction Treatment on CO Sensing Properties of SnO₂-based Gas Sensor

Abstract

Response of SnO₂-based sensors to CO under extreme conditions was investigated. It was found that Pd and V₂O₅-loaded SnO₂ device (thick film), after a reduction treatment in CO flow, showed reverse response to dilute CO (increase in resistance) under particular operating conditions, i.e., lower temperature below 325°C, low humidity less than 100 Pa water vapor pressure. The reverse response tended to be more conspicuous as the CO concentration decreased and the coexistent O₂ partial pressure increased. Similar reduction-induced reverse response to CO was also observed with Pd-loaded SnO₂ device. XPS analysis suggested that the reverse response should be related with the oxidation state of SnO₂.