The oxygen partial pressure in solid oxide electrolysis cells with multilayer electrolytes

A number of degradation mechanisms have been observed during the long-term operation of solid oxide electrolysis cells (SOEC). Using an electrolyte charge carrier transport model and a diffuse interface treatment for a multilayer electrolytes, we quantify the oxygen potentials across the electrolyte and thereby provide insights into these degradation mechanisms. Our model describes the transport of charge carriers in the electrolyte when the oxygen partial pressure is extremely low by accounting for the spatial variation of the concentration of oxygen vacancies in the electrolyte which is closely related to the degradation of the SOEC near the interface of hydrogen electrode and electrolyte. Moreover, we identify four quantities that characterize the distribution of oxygen partial pressure in the electrolyte, which are directly related to the degradation mechanisms in the electrolyte as well, and give analytical estimates for them. These analytical expressions provide guidance on the parameters that need to be controlled to suppress the degradation observed in the electrolyte. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study uses an electrolyte charge carrier transport model and a diffuse interface treatment for multilayer electrolytes to quantify oxygen potentials and provide insights into degradation mechanisms observed during long-term operation of solid oxide electrolysis cells (SOEC). The model describes the transport of charge carriers in the electrolyte and identifies quantities characterizing the distribution of oxygen partial pressure in the electrolyte, which are directly related to degradation mechanisms. Analytical estimates are provided for guidance on parameters needed to suppress degradation in the electrolyte.