Potentiometric Carbon Monoxide Sensors Using an Anion-Conducting Polymer Electrolyte and Au-Loaded SnO2Electrodes

Potentiometric gas sensors using an anion-conducting polymer as an electrolyte and SnO 2 loaded with or without 2.0 wt% Au as an electrode material were fabricated and the CO-sensing properties were investigated mainly in wet synthetic air (57%RH) at 30°C. Loading of Au onto SnO 2 powders by precipitation-deposition technique was quite effective in improving the sensing properties to CO and H 2 , and the magnitude of CO response was larger than that of H 2 response. In addition, the CO response was largely dependent on concentration of O 2 in the gaseous atmosphere. These results indicate that electromotive force of the sensor is probably determined by mixed potential resulting from CO oxidation and O 2 reduction. Heat treatment of the Au-loaded SnO 2 powder under reducing atmosphere decreased the H 2 -sensing properties, and thus largely enhanced the CO selectivity against H 2 . Especially, the sensor using Au-loaded SnO 2 which was heat-treated in H 2 at 250°C showed large CO response, the largest CO selectivity against H 2 , and the fastest response and recovery speeds among all the sensors tested, while storage of the sensor under normal atmosphere weakened the effect of the heat-treatment in H 2 at 250°C on the CO-sensing properties.