A review on micro-level modeling of solid oxide fuel cells

• Micro-modeling of SOFCs through advanced microstructural characterization.
• FIB-SEM and X-ray nanotomography are the most common methods for visualization.
• Linking microstructural properties from 3D reconstruction to experimental data.
• Strong relation between the SOFC performance and the active TPB density.

Solid oxide fuel cells (SOFCs) are ceramic based electrochemical devices operating at high temperatures and generates electricity and useful heat energy utilizing various fuels at a high efficiency. The main structure of the cell comprises a dense electrolyte coated with two porous anode and cathode electrodes. The electrolyte is responsible for the transfer of oxide ion while the electrochemical reactions take place in the electrodes. The cell performance is limited by the number of reaction zones known as triple/three phase boundaries (TPBs). Therefore, the electrodes play a crucial role in achieving high power as well as long service life. When the requirements that SOFC electrodes should meet are considered, the most successful electrode materials seem to be composite ones, including ionic and electronic conductive phases with pores for the gas transport. However, this combination is not enough alone since the contiguous contact of these three phases within the electrodes is also necessary to obtain electrochemically active reaction zones. The number of these areas can be a useful metric for predicting the cell performance or provide a relationship between the performance and microstructure. The determination of the electrochemical reaction zones at the micro-scale and the microstructural parameters influencing their density are required to link the microstructure to the performance. Therefore, in this paper, micro-modeling studies of SOFC electrodes through advanced microstructural characterization are reviewed.