Modeling the Distribution of Oxygen Partial Pressure in the Electrolyte of Solid Oxide Cells and Its Implication on Microstructure Evolution in the Hydrogen Electrode

Abstract

The distribution of oxygen partial pressure in the electrolyte has an important effect on the stability of solid oxide cells (SOCs). It is well known that the high oxygen partial pressure at the oxygen electrode and electrolyte interface causes delamination, while its effect in the hydrogen electrode (HE) has received comparatively little attention. The only existing model for the distribution of oxygen partial pressure in the electrolyte of SOC is proposed by Virkar et al., which is a one-dimensional model that does not consider the Butler-Volmer equation at triple phase boundary (TPB) nor the microstructure’s effect. In this work, the Virkar’s model was extended to three dimensions and the Butler-Volmer equation was added at TPB to investigate the distribution of oxygen partial pressure in the actual electrode microstructure. The oxygen partial pressure in the yttria-stabilized-zirconia (YSZ) phase of HE near the HE-electrolyte interface was found to be significantly greater than the oxygen partial pressure in the pore phase of HE, which may lead to Ni oxidation. Furthermore, a phase field model was employed to simulate the microstructural evolution of Ni particles on YSZ surfaces with the assumption that NiO forms at the Ni-YSZ interface. The NiO formation affects the microstructure evolution in HE by changing the shape of the Ni particles.