Impedance Spectra of Activating/Passivating Solid Oxide Electrodes

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Abstract

The aim of this paper is to show that the inductive arcs seen in electrochemical impedance spectra of solid oxide cells (SOCs) are real electrochemical features that in several cases can be qualitatively explained by passivation/activation processes.
Several degradation processes of Solid Oxide Fuel Cells (SOFC) and Electrolyser Cells (SOEC) exist. Not all of them are irreversible, especially not over short periods. A reversible degradation is termed “passivation” and the reverse is then “activation”. These processes may exhibit themselves in the Electrochemical Impedance Spectra (EIS) as inductive arcs at low frequencies, often below 1 Hz.
The phenomenon has been observed and reported in the literature far back in time, for a large variety of electrodes and in many different circumstances. Examples of such EIS of SOC electrodes are shown and discussed. EIS of both technological and model electrodes are presented. The inductive arcs in the EIS of the porous technological electrode are usually less pronounced compared to model electrodes. Inductive arcs in EIS of both H2 and O2 electrodes in SOCs are treated here and for both cases the inductive arcs are explained by i-V curves that are not reflecting really stable electrode performance. This is in line with frequent observations of oscillating current density at electrode potentials in the vicinity of the ranges in which the inductive arcs are observed.
Original languageEnglish
Title of host publicationProceedings of 11th European SOFC and SOE Forum 2014
Number of pages10
PublisherEuropean Fuel Cell Forum
Publication date2014
Article numberB1209
ISBN (Electronic)3-905592-16-9
Publication statusPublished - 2014
EventEuropean fuel cell 2014 - 11th European SOFC and SOE Forum 2014 - Lucerne, Switzerland
Duration: 1 Jul 20144 Jul 2014

Conference

ConferenceEuropean fuel cell 2014 - 11th European SOFC and SOE Forum 2014
CountrySwitzerland
CityLucerne
Period01/07/201404/07/2014

Cite this

Mogensen, M. B., Sun, X., Koch, S., Graves, C. R., & Hansen, K. V. (2014). Impedance Spectra of Activating/Passivating Solid Oxide Electrodes. In Proceedings of 11th European SOFC and SOE Forum 2014 [B1209] European Fuel Cell Forum.