Promoting selectivity and sensitivity for a high temperature YSZ-based electrochemical total NOx sensor by using a Pt-loaded zeolite Y filter

Potentiometric sensors provide a promising approach for NO(x) detection in harsh environments, but typically suffer from interferences with other gases. Potentiometric sensors use two electrodes, and both chemical and electrochemical reactivity at each electrode are critical to sensor performance. In this study, we have examined Pt electrode covered with Pt containing zeolite Y (PtY) and WO(3) as the two electrode materials. Temperature programmed desorption of NO from NO(x)/O(2) -exposed PtY and WO(3) was studied. Inaddition, the ability of PtY and WO(3) to equilibrate a mixture of NO and O(2) was examined over the temperature range of 200-600 degrees C. Significant reactivity differences were found between PtY and WO(3), with the latter being largely inactive toward NO(x) equilibration. With gases passing through a PtY filter, it was possible to remove interferences from 2000 ppm CO, 800 ppm propane, 10 ppm NH(3), as well as minimize effects of 1-13 % O(2), CO(2), and H(2)O. By maintaining a temperature difference between the filter (typically at 400 degrees C) and the sensor at 600 degrees C, total NO(x) concentration (NO + NO(2)) was measured. By connecting three sensors in series, the sensitivity was also significantly improved. (c) 2007 Elsevier B.V. All rights reserved.