Design of High-Performance Environmental Gas Sensors Using Solid Electrolytes and Multi-Component Auxiliary Electrodes

点击翻译按钮获取中文摘要

Sensing properties of solid electrolyte oxygenic gas sensor were greatly improved by using multi-component auxiliary electrode. 1. The use of a binary nitrate electrode of NaNO_3-Ba(NO_3)_2 for solid electrolyte NO_2 sensor made it possible to stand operation at higher temperature up to 500ﾟC,as well as to suppress the interference of water vapor. An NO_2 sensor using Ba(NO_3)_2 auxiliary electrode and Ba-beta/beta"-alumina was found to show quicker responses and to stand higher temperature operation. A NASICON-based solid electrolyte device fitted with an NaNO_2 auxiliary electrode showed excellent sensing characteristics to NO and NO_2 in air,i.e., the electromotive force (EMF) followed the Nernt's equation for 1 - 800 ppm NO and 0.1 - 200 ppm NO_2 at temperatures of 150-240ﾟC. The response of these sensors were found to be totally independent of coexisting oxygen. 2. A NASICON-based CO_2 sensor was greatly improved in response and water vapor-resistance by using binary carbonate ele … More ctrodes of Na_2CO_3-BCO_3(B=Ca,Sr,Ba). These sensors could respond very well to CO_2 in air over a wide temperature range of 270-600ﾟC. The CO_2 sensor was further improved in stability by using Li-based binary carbonate electrodes of Li_2CO_3-BCO_3(B=Ca,Sr,Ba). The sensor responses, EMF, to varying partial pressure of CO_2 were in accordance with a 2-electron reaction of CO_2, while the response to a fixed P_<CO2> was found to be almost independent of partial pressure of O_2 at temperatures above 450ﾟC, while at 305ﾟC and below, it dependent on P_<O2> in a manner similar to a 2- electron reaction of O_2. Thus, two-types of sensing electrode reactions including peroxycarbonate or peroxide were indicated to occur depending on working temperature. 3. Electrochemical cells using MgO-stabilized zirconia tube coated with metal sulphates were found to exhibit fairly good sensing properties to 20-200 ppm SO_2 in air at 650-800ﾟC. SO_x sensor using Li_2SO_4-CaSO_4-SiO_2 auxiliary electrode showed quicker response, 90% response and 90% recovery time to 20 ppm SO_2 at 650ﾟC were 10_s and 7 min, respectively. This sensor exhibits excellent selectivity and good stability in long-term operation. Less