Performance evaluation of SO x ( x = 2,3) gas sensors using Ag-β′'-alumina solid electrolyte

Abstract

Fully solid state SO x sensors have been investigated with a galvanic cell of Pt, Ag/Ag-β′'-alumina/SO 3, SO 2, O 2, Pt using tubular Ag-β′'-alumina as solid electrolyte, metal silver as solid reference electrode, and porous Pt as working electrode. The values of electric motive force (EMF) of the sensors are consistent with the theoretically calculated ones at temperatures above 550 °C in the p SO x range of at least 10–50 000 ppm. Applying catalysts such as Pt-net and V 2O 5 in the gas upstream considerably improves the sensor performance and extend its working temperature down to 450 °C. The reproducible EMF values are obtained in the gas flow velocity of 0.2–0.4 cm/s. The response time of the sensors is 50–100 s as the p SO x changes. The sensors exhibit a good selectivity to SO x against hundred-fold concentrations of CO 2, NO 2 and H 2O.