Performance and Durability of Solid Oxide Electrolysis Cells

Abstract

Solid oxide fuel cells produced at Risø National Laboratory have been tested as electrolysis cells by applying an external voltage. Results on initial performance and durability of such reversible solid oxide cells at temperatures from 750 to 950°C and current densities from −0.25 A/cm 2 to − 0.50 A/cm 2 are reported. The full cells have an initial area specific resistance as low as 0.27 ⍀cm 2 for electrolysis operation at 850°C. During galvanostatic long-term electrolysis tests, the cells were observed to passivate mainly during the first ϳ100 h of electrolysis. Cells that have been passivated during electrolysis tests can be partly activated again by operation in fuel cell mode or even at constant electrolysis conditions after several hundred hours of testing.

Solid Oxide Electrolysis Cells: Microstructure and Degradation of the Ni/Yttria-Stabilized Zirconia Electrode

“…19,26 The start-up procedure, including heating ramp ͑1°C/min to 1000°C͒, reduction procedure ͑9% H 2 in N 2 and pure H 2 ͒, and initial characterization of the cell performance ͑i-V curves in fuel cell and electrolysis mode and electrochemical impedance spectroscopy͒ are described elsewhere. 12,26 The electrolysis tests were performed galvanostatic. An overview of the long-term electrolysis test specifications and duration is given in Table I.…”

“…However, the cells can be partly reactivated either by fuel cell operation of the cell or continued galvanostatic electrolysis operation at constant conditions. 12 Postmortem analyses of tested SOECs showed that significant amounts of impurities had segregated to the hydrogen electrode/electrolyte interface of heavily passivated SOECs. It was proposed that at least a part of these impurities originated from the applied albite glass sealing used in the setup for cell testing.…”

Mechanism and Kinetics of Ni-Y2O3-ZrO2Hydrogen Electrode for Water Electrolysis Reactions in Solid Oxide Electrolysis Cells

“…Solid oxide electrolysis cell (SOEC) as an electrochemical device to convert electricity of renewable energy sources such as solar energy, wind power, hydropower and geothermal power into chemical energy of fuels such as hydrogen and syngas has attracted increasing interests due to the depleting fossil fuel sources, high oil prices and environmental considerations. [1][2][3][4][5][6][7] In the case of water electrolysis to produce hydrogen, steam is introduced to the hydrogen electrode side where it is reduced to hydrogen, while the oxygen ions are migrated through the electrolyte to the air electrode side where they combine to form pure oxygen. Co-electrolysis of steam and CO 2 in an SOEC yields synthesis gas (CO+H 2 ) which in turn can be catalysed to various types of synthetic fuels (such as methane and methanol).…”

Solid oxide electrochemical reactor science.

“…Hauch et al found in degradation tests from 750 °C to 950 °C and current densities from -0.25 A/cm 2 to -0.5 A/cm 2 (negative sign indicating cathodic polarization) that cell passivation mainly occurred in the first 100 h of electrolysis operation, with less passivation noted at higher temperatures. Much of the degradation was attributed to migration of impurities from glass sealing [20]. In a follow-on publication, the glass seal was replaced with a gold foil and platinum paste seal to remove the possibility of silica impurities.…”