Zeolites for Sensors for Reducing Gases

摘要

Due to their unique properties, zeolites can be used either as passive filters to greatly enhance selectivity or as very selective sensor materials. Some well known principles are briefly reviewed and the following three novel application modes are discussed. Zeolites can be applied as cover layers for specificity improvement of p-type semiconducting hydrocarbon sensors. Furthermore, a novel combination of metal oxides with zeolites leading to a very selective hydrocarbon sensor is described. In this application, it is shown that the interface chromium oxide / zeolite plays an essential role. And, in a very recent approach, Na~+ ion conducting zeolites are applied as an auxiliary phase in a potentiometric gas sensor. The cell voltage shows a Nernstian response, which is selective towards propane. Here, the proposed mechanism assumes Na~+ activity changes in the zeolite pores due to hydrocarbon sorption.