Engineering nanostructured fuel electrodes for high-performance, durable SOCs through infiltration

This chapter presents the assessment of the various groups of infiltrated solid oxide cell (SOC) fuel electrodes together with the infiltration technique. First, the fundamental principles of the SOC and the state-of-the-art fuel electrode materials and their limitations are outlined. In order to further improve the electrochemical performance and durability of an SOC, the infiltration technique has been applied as an effective method for modifying the microstructure of the porous fuel electrode backbone that could result in extended electrocatalytic active sites. The infiltration procedure, different infiltration methods, and key process parameters, such as precursor chemistry, heat treatment temperature and number of infiltration cycles, are briefly discussed and a summary of the process parameters based on experimental data from previous reports is presented. The performance and/or durability of the SOCs with electrocatalyst infiltrated fuel electrodes are reviewed according to the type of fuel electrodes, e.g., cermet-based and oxide-based fuel electrodes. For instance, the infiltrated Ni-based cermet fuel electrodes are discussed considering different factors such as improving sulfur tolerance or resistance to carbon deposition for hydrocarbon fuel utilization, decreasing the polarization resistance or area-specific resistance, and improving the cell performance for steam, CO₂, or co-electrolysis operations. In addition, modification of perovskite or fluorite-based fuel electrodes by introducing active metals and/or metal oxides is also briefly discussed. Finally, the ongoing challenges and opportunities of the infiltration method in terms of scalability and industrialization of infiltrated SOCs are outlined in the outlook.