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CAUSES OF DEGRADATION IN A SOLID OXIDE ELECTROLYSIS STACK
Causes of degradation in a solid oxide electrolysis stack
J. David Carter, Jennifer Mawdsley, A. Jeremy Kropf
Argonne National Laboratory, Argonne, Illinois, USA
Abstract
Steam electrolysis experiments conducted at Idaho National Laboratory (INL) have demonstrated an
efficient process to generate hydrogen using waste heat and electricity from a nuclear power plant.
However, the hydrogen output was observed to decrease significantly over time. Solid oxide stack
components from the INL studies were analysed at Argonne National Laboratory to elucidate the
degradation mechanisms of electrolysis. After probable regions of degradation were identified by
surface techniques, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy
(EDS) were used to further characterise the causes of degradation by examining cross-sections of stack
components.
The main causes of degradation come as a result of the cells operating in electrolysis mode, since the
same cells operating in the fuel cell mode exhibit stable performance. From this study, we identified
five causes that contribute to degradation: i) Cracks were observed along the conductive bond layer/
interconnect interface in the oxygen electrode compartment. ii) Chromium was observed to substitute
for cobalt in the bond layer reducing its conductivity. iii) Densification and delamination were observed
by the oxygen electrode. iv) A Si/Mn capping layer was observed within millimeters of the sealing edge
of the steam/hydrogen electrode, and Si was distributed throughout the electrode. v) Non-conductive
interface layers formed at the interconnect/flow field interface in the steam/hydrogen electrode
compartment.
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