Degradation Mechanisms of SOECs

Oxygen partial pressure distribution in the electrolyte

It is found in experiments that SOECs with an CGO inter-diffusion barrier sandwiched between the YSZ electrolyte and an LSCF-CGO oxygen electrode shows a significantly lower degradation rate, including less severe crack propagation in YSZ electrolyte and less severe Ni-YSZ electrode degradation, comparing with cells with pure YSZ electrolyte and an LSM-YSZ oxygen electrode. According to former experimental and theoretical works, some degradation mechanisms are connected to the distribution of oxygen partial pressure and concentration of oxygen vacancies in the electrolyte under solid oxide electrolysis operating mode. However, these quantities are hard be measured in the experiments. In this project, we worked on quantitative modeling on gas transportation and chemical reactions at the electrodes, which determines the polarization resistance, and the transport of species (oxygen ion, electrons and holes) in the multi-layer electrolyte of solid oxide electrolyzer cells, in order to understand the degradation mechanisms and optimize the design of the structure of electrolyte and electrodes to achieve expected durability under required operation condition (low temperature and high current density). This is a joint project with Prof. Scott Barnett’s group.

Participants

• Qian Zhang, Ph.D.

Selected Publications

Qian Zhang, Qin-Yuan Liu, Beom-Kyeong Park, Scott Barnett and Peter Voorhees , “The oxygen partial pressure in solid oxide electrolysis cells with multilayer electrolytes”, Acta Materialia, 213, 116928 (2021), doi: 10.1016/j.actamat.2021.116928

Qian Zhang, Boem-Kyeong Park, Scott Barnett and Peter Voorhees, “On the role of the zirconia/ceria interface in the degradation of solid oxide electrolysis cells”, Appl. Phys. Lett. 117, 123906 (2020), doi: 10.1063/5.0016478 [Editor’s Pick]

Beom-Kyeong Park, Qian Zhang, Peter W. Voorhees and Scott Barnett, “Conditions for stable operation of solid oxide electrolysis cells: oxygen electrode effects”, Energy Environ. Sci., 2019, 12, 3053–3062 doi: 10.1039/C9EE01664C

Nickel migration in Nickel/YSZ/pore electrode

In the Nickel/YSZ/Pore electrode in solid oxide fuel cells, one of the most commonly observed degradation phenomenon is Nickel depletion at the interface of electrode and electrolyte. According to experimental observations and measurements, a change in Nickel contact angle near the electrolyte during electrolysis can be introduced due to either a change in fuel composition, i.e., steam depletion near the electrolyte or a change in the electrical potential in the electrode. In order to determine whether a change in Ni wetting angle with position in the Ni-YSZ electrode can explain the observed depletion of Ni from the near-electrolyte region of the Ni-YSZ fuel electrode, a phase field model is proposed to study migration of Ni particles in the Ni/YSZ/Pore electrode. Influence of morphological properties of the Ni/YSZ/pore electrode on Ni migration is studied by theoretical analysis, numerical simulations, data analysis and machine learning. This is a joint project with Prof. Scott Barnett’s group and Prof. Katsuyo Thorton’s group in University of Michigan.

Participants

• Qian Zhang, Ph.D.

Selected Publications

Qian Zhang, Scott Barnett and Peter Voorhees, Migration of Inclusions in A Matrix Due To A Spatially Varying Interface Energy, under revision in Scripta Materialia (2021)