Idaho National Laboratory (INL) is performing high-temperature electrolysis research to generate hydrogen using solid oxide electrolysis cells (SOECs). The project goals are to address the technical and degradation issues associated with the SOECs. This paper provides a summary of various ongoing INL and INL sponsored activities aimed at addressing SOEC degradation. These activities include stack testing, post-test examination, degradation modeling, and a list of issues that need to be addressed in future. Major degradation issues relating to solid oxide fuel cells (SOFC) are relatively better understood than those for SOECs. Some of the degradation mechanisms in SOFCs include contact problems between adjacent cell components, microstructural deterioration (coarsening) of the porous electrodes, and blocking of the reaction sites within the electrodes. Contact problems include delamination of an electrode from the electrolyte, growth of a poorly (electronically) conducting oxide layer between the metallic interconnect plates and the electrodes, and lack of contact between the interconnect and the electrode. INL’s test results on high temperature electrolysis (HTE) using solid oxide cells do not provide clear evidence of whether different events lead to similar or drastically different electrochemical degradation mechanisms. Post-test examination of the solid oxide electrolysis cells showed that the hydrogen electrode and interconnect get partially oxidized and become nonconductive. This is most likely caused by the hydrogen stream composition and flow rate during cool down. The oxygen electrode side of the stacks seemed to be responsible for the observed degradation due to large areas of electrode delamination. Based on the oxygen electrode appearance, the degradation of these stacks was largely controlled by the oxygen electrode delamination rate. Virkar and co-workers have developed a SOEC model based on concepts in local thermodynamic equilibrium in systems otherwise in global thermodynamic nonequilibrium. This model is under continued development. It shows that electronic conduction through the electrolyte, however small, must be taken into account for determining local oxygen chemical potential, within the electrolyte. The chemical potential within the electrolyte may lie out of bounds in relation to values at the electrodes in the electrolyzer mode. Under certain conditions, high pressures can develop in the electrolyte just under the oxygen electrode (anode)/electrolyte interface, leading to electrode delamination. This theory is being further refined and tested by introducing some electronic conduction in the electrolyte.

References

References
1.
Lewis
,
D.
, 2008, “
Hydrogen and Its Relationship with Nuclear Energy
,”
Prog. Nucl. Energy
,
50
, pp.
394
401
.
2.
Forsberg
,
C. W.
, 2005,
“Nuclear Hydrogen Production for Liquid Hydrocarbon Transport Fuels,” Proceedings, AIChE Annual Meeting
, pp.
7988
7995
.
3.
Gazzarri
,
J. I.
, 2007,
“Impedance Model of a Solid Oxide Fuel Cell for Degradation Diagnosis,”
Ph.D. thesis, The University of British Columbia, Vancouver, Canada.
4.
Guan
,
J.
,
et al.
, 2006. “High Performance Flexible Reversible Solid Oxide Fuel Cell,” GE Global Research Center Final Report for DOE Cooperative Agreement No. DE-FC36-04GO-14351, NTIS Order No. DE2007-899650.
5.
Hauch
,
A.
,
Jensen
,
S. H.
,
Menon
,
M.
, and
Mogensen
,
M.
, 2005,
“Stability of Solid Oxide Electrolyser Cells,” Risø International Energy Conference
,
L. S.
Petersen
and
H.
Larsen
, eds., 23–25 May, 2005,
Roskilde, Denmark
.
6.
Hauch
,
A.
, 2007,
“Solid Oxide Electrolysis Cells—Performance and Durability,”
Ph.D. thesis, Technical University of Denmark, Risø National Laboratory, Roskilde, Denmark.
7.
Hauch
,
A.
,
Jensen
,
S. H.
,
Ebbesen
,
S. D.
, and
Mogensen
,
M.
, 2007,
“Durability of Solid Oxide Electrolysis Cells for Hydrogen Production,” Risø International Energy Conference
,
L. S.
Petersen
and
H.
Larsen
, eds.,
Roskilde, Denmark
, 2007.
8.
Hauch
,
A.
Ebbesen
,
S. D.
Jensen
,
S. H.
, and
Mogensen
,
M.
, 2008, “
Solid Oxide Electrolysis Cells: Microstructure and Degradation of the Ni/Yttria-Stabilized Zirconia Electrode
,”
J. Electrochem. Soc.
,
155
(
11
), pp.
B1184
B1193
.
9.
O’Brien
,
J. E.
Stoots
,
C. M.
Herring
,
J. S.
Condie
,
K. G.
, and
Housley
,
G. K.
, 2009,
“The High-Temperature Electrolysis Program at the Idaho National Laboratory: Observations on Performance Degradation,” High Temperature Water Electrolysis Limiting Factors
,
Eifer, Karlsruhe, Germany
, June 9–10.
10.
Haering
,
C.
,
Roosen
,
A.
,
Schichl
,
H.
, and
Schnoller
,
M.
, 2005, “
Degradation of the Electrical Conductivity in Stabilized Zirconia System Part II: Scandia-Stabilised Zirconia
,”
Solid Sate Ionics
,
176
(
3-4
), pp.
261
268
.
11.
O’Brien
,
J. E.
,
Stoots
,
C. M.
,
Herring
,
J. S.
, and
Hartvigsen
,
J. J.
, 2007, “
Performance of Planar High-Temperature Electrolysis Stacks for Hydrogen Production from Nuclear Energy
,”
Nucl. Technol.
,
158
, pp.
118
131
.
12.
Carter
,
D. J.
et al.
, 2008,
“Determining Causes of Degradation in High Temperature Electrolysis Stacks,” presented at the Workshop on Degradation in Solid Oxide Electrolysis Cells and Strategies for its Mitigation, Fuel Cell Seminar & Exposition
, October 27-30, 2008,
Phoenix, AZ
.
13.
Mawdsley
,
et al.
2007.
“Post-Test Evaluation of the Oxygen Electrode from a Solid Oxide Electrolysis Stack and Electrode Materials Development,” AIChE Annual Meeting
,
Salt Lake City, UT
, November 4–9.
14.
Mawdsley
,
J. R.
,
Carter
,
J. D.
,
Kropf
,
A. J.
,
Yildiz
,
B.
, and
Maroni
,
V. A.
, 2009, “
Post-test Evaluation of Oxygen Electrodes from Solid Oxide Electrolysis Stacks
,”
Int. J. Hydrogen Energy
,
34
(
9
), pp.
4198
4207
.
15.
Sharma
,
V. I.
, and
Yildiz
,
B.
, 2009,
“Degradation Mechanisms in La0.8Sr0.2CoO3 Oxygen Electrode Bond Layer in Solid Oxide Electrolytic Cells,”
MIT Subcontract Report to INL.
16.
Sharma
,
V. I.
, and
Yildiz
,
B.
, 2010, “
Degradation Mechanism in La0.8Sr0.2CoO3 as Contact Layer on the Solid Oxide Electrolysis Cell Anode
,”
J. Electrochem. Soc.
,
157
(
3
), pp.
B441
B448
.
17.
Virkar
,
A. V.
, 2005, “
Theoretical Analysis of the Role of Interfaces in Transport through Oxygen Ion and Electron Conducting Membranes
,”
J. Power Sources
,
147
, pp.
8
31
.
18.
Virkar
,
A. V.
, 2007, “
A Model for Solid Oxide Fuel Cell (SOFC) Stack Degradation
,”
J. Power Sources
,
172
, pp.
713
724
.
19.
Lim
,
H.-T.
, and
A. V.
Virkar
,
A. V.
, 2008, “
A Study of Solid Oxide Fuel Cell Stack Failure by Inducing Abnormal Behavior in a Single Cell Test
,”
J. Power Sources
,
185
, pp.
790
800
.
20.
Virkar
,
A. V.
, 2010, “
Mechanism of Oxygen Electrode Delamination in Solid Oxide Electrolyzer Cells
,”
Int. J. Hydrogen Energy
,
35
(
18
), pp.
9527
9543
.
21.
Sohal
,
M. S.
, 2009,
“Degradation in Solid Oxide Cells during High Temperature Electrolysis,”
Idaho National Laboratory Report No. INL/EXT-09-15617.
22.
Sohal
,
M. S.
,
O’Brien
,
J. E.
,
Stoots
,
C. M.
,
Herring
,
J. S.
,
Hartvigsen
,
J.
,
Larsen
,
D.
,
Elangovan
,
S.
,
Carter
,
J. D.
,
Sharma
,
V. I.
, and
Yildiz
,
B.
, 2009,
“Critical Causes of Degradation in Integrated Laboratory Scale Cells during High-Temperature Electrolysis,”
Idaho National Laboratory Report No. INL/EXT-09-16004.
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