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A parameter study of solid oxide electrolysis cell degradation: Microstructural changes of the fuel electrode

Hörlein, Michael and Riegraf, Matthias and Costa, Rémi and Schiller, Günter and Friedrich, K. Andreas (2018) A parameter study of solid oxide electrolysis cell degradation: Microstructural changes of the fuel electrode. Electrochimica Acta, 276, pp. 162-175. Elsevier. doi: 10.1016/j.electacta.2018.04.170. ISSN 0013-4686.

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A parameter study of 20 solid oxide electrolysis cells was carried out to systematically investigate long-term degradation each over 1,000 h under variation of temperature, humidity and current density. The influence of operating temperature was investigated between 750 and 850 °C, the humidity ranged from 40 % to 80 % H2O, and the current density varied between open circuit voltage (OCV) and 1.5 A·cm–2. The progress of degradation was monitored in-situ by electrochemical impedance spectroscopy. Five different contributions to the spectra were identified by calculating the distribution of relaxation times and separated via a complex non-linear square fitting routine. The present work focuses on the degradation of the fuel electrode. From SEM analysis, Ni depletion and an increased pore fraction close to the electrode/electrolyte interface was derived, which is correlated with an increased ohmic resistance of the cells. This unidirectional transport of Ni away from the fuel electrode/electrolyte interface leads to an effective electrolyte extension and is the main source of degradation. Ni depletion is shown to be driven by current density and its extent is shown to be dependent on the complex interplay between the operating parameters current density, anode overpotential, humidity and temperature. It is particularly pronounced for pH2O larger than 0.8 atm and temperatures above 800 °C. Furthermore, the fuel electrode electrochemistry also exhibits degradation in the high-frequency region around 10 exp4 Hz.

Item URL in elib:https://elib.dlr.de/123148/
Document Type:Article
Title:A parameter study of solid oxide electrolysis cell degradation: Microstructural changes of the fuel electrode
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Hörlein, Michaelmichael.hoerlein (at) dlr.deUNSPECIFIED
Riegraf, Matthiasmatthias.riegraf (at) dlr.dehttps://orcid.org/0000-0002-0383-2545
Costa, Rémiremi.costa (at) dlr.dehttps://orcid.org/0000-0002-3534-1935
Schiller, GünterGuenter.Schiller (at) dlr.dehttps://orcid.org/0000-0001-5093-7625
Friedrich, K. Andreasandreas.friedrich (at) dlr.dehttps://orcid.org/0000-0002-2968-5029
Journal or Publication Title:Electrochimica Acta
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1016/j.electacta.2018.04.170
Page Range:pp. 162-175
EditorsEmailEditor's ORCID iD
Series Name:Elsevier
Keywords:Solid oxide electrolysis cells (SOEC), Ni/YSZ electrode, Degradation, Electrochemical impedance spectroscopy, Ni depletion
HGF - Research field:Energy
HGF - Program:Storage and Cross-linked Infrastructures
HGF - Program Themes:Electrolysis and Hydrogen
DLR - Research area:Energy
DLR - Program:E SP - Energy Storage
DLR - Research theme (Project):E - Elektrochemical Processes (Electrolysis) (old)
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Electrochemical Energy Technology
Deposited By: Schiller, Dr.rer.nat. Günter
Deposited On:19 Dec 2018 17:04
Last Modified:01 Feb 2020 03:00

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