Carbon Deposition in Solid Oxide Cells during Co-Electrolysis of H2O and CO2

Youkun Tao, Sune Dalgaard Ebbesen, Mogens Bjerg Mogensen

Research output: Contribution to journalConference articleResearchpeer-review

Abstract

Carbon formation during co-electrolysis of H2O and CO2 in Ni-YSZ supported Solid Oxide Electrolysis Cells (SOECs) may occur, especially at high current density and high conversion. In order to evaluate the carbon formation limits, five galvanostatic tests were performed in this work at electrolysis current densities from 1.5 to 2.25 A/cm2 and reactant (H2O + CO2) conversion of up to 67%. Delamination and carbon nano-fibers were observed at the Ni-YSZ|YSZ interface for two cells with a dense microstructure operated at electrolysis current densities of 2.0 and 2.25 A/cm2 and a conversion of 59% and 67% respectively. Based on the nominal gas composition, carbon formation only occurs, according to equilibrium thermodynamics, at a reactant conversion above 99%. Therefore, the observed carbon formation is ascribed to a change in gas composition due to the diffusion limitations within the Ni-YSZ support and the active Ni-YSZ electrode. Carbon nano-fibers were only observed close to the YSZ electrolyte, indicating a very reducing atmosphere and a large over-potential gradient in the active electrode, being highest at the interface to the bulk electrolyte and decreasing toward the Ni-YSZ support.
Original languageEnglish
JournalJournal of the Electrochemical Society
Volume161
Issue number3
Pages (from-to)F337-F343
ISSN0013-4651
DOIs
Publication statusPublished - 2014
EventPacific Rim Meeting on Electrochemical and Solid-State Science: 222nd Meeting of ECS — The Electrochemical Society and 2012 Fall Meeting of The Electrochemical Society of Japan - Hawaii Convention Center and the Hilton Hawaiian Village, Honolulu, United States
Duration: 7 Oct 201212 Oct 2012
http://www.electrochem.org/meetings/biannual/222/222.htm

Conference

ConferencePacific Rim Meeting on Electrochemical and Solid-State Science
LocationHawaii Convention Center and the Hilton Hawaiian Village
CountryUnited States
CityHonolulu
Period07/10/201212/10/2012
Internet address

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