Proton-conducting oxide with redox protonation and its application to a hydrogen sensor with a self-standard electrode

Abstract

In order to simplify the structure of the EMF-type hydrogen sensor using a proton conductor as the electrolyte, an electrolyte serving as a self-standard electrode in air was developed. The electrochemical properties and proton dissolution mechanism of Mn-doped CaZrO₃ were evaluated by impedance analysis, EMF measurement, IR absorption analysis and ESR measurement. Mn-doped CaZrO₃ acquires a proton from hydrogen by reduction of the manganese ion. 5 mol% Mn doped CaZrO₃ showed proton conduction in a reducing atmosphere and hole conduction in an oxidizing atmosphere. A gas concentration cell using CaZr_0.95Mn_0.05O_3−δ as the electrolyte was constructed for use as a hydrogen sensor. It was found to be dependent only on the hydrogen potential of the working electrode when air was used as the reference gas.