Microstructural and surface engineering of fuel electrodes for enhanced high-temperature CO₂ electrolysis

In recent years, solid oxide cells (SOCs) have emerged as promising high-temperature electrochemical devices for efficient power generation and electrolysis of H₂O and CO₂ to produce hydrogen and syngas. However, their widespread deployment remains limited by challenges in materials processing, electrode microstructural engineering, and long-term stability. Continued efforts are therefore needed to establish environmentally friendly, scalable fabrication routes, design porous ceramic electrodes with optimized structures, and develop robust surface-modification strategies. This thesis connects aqueous ceramic processing, porous-electrode microstructural engineering, and CeO₂-based surface modification to the electrochemical performance of SOCs. First, an aqueous tape-casting method was developed for YSZ, ScSZ, and LSGM electrolytes. Powder pretreatment, slurry rheology, drying, and sintering were systematically investigated, establishing processing windows for thin, dense, and mechanically robust electrolyte sheets. Second, porous LSCM/ScSZ fuel-electrode backbones were fabricated without sacrificial pore formers using particle-size grading of pre-sintered LSCM powders. SEM and quantitative image analysis were used to determine porosity, pore-size distribution, and tortuosity, while electrochemical impedance spectroscopy assessed the effects of tailored microstructures on electrode polarisation. Third, Zr-doped CeO₂ (ZDC; Zr₀.₁Ce₀.₉O₂₋δ) was infiltrated into porous LSCM/ScSZ scaffolds to enhance CO₂ electrocatalytic activity. Contact-angle measurements guided precursor optimization, while SEM, XPS, and Raman spectroscopy revealed the evolution of ZDC morphology and defect chemistry. Single-cell EIS and DRT analysis showed reduced fuel-electrode polarisation after ZDC impregnation. Finally, Ru-modified GDC/YSZ fuel electrodes were developed for CO/CO₂ redox operation. Their phase structure, microstructure, and electrochemical performance were systematically evaluated. EIS and DRT analysis showed that Ru modification significantly reduced fuel-electrode polarisation by promoting CO activation and CO/CO₂ surface redox kinetics on the GDC-based electrode. Overall, this work provides practical guidelines for eco-friendly SOC fabrication and rational electrode microstructural design, while demonstrating the potential of CeO₂-based modifiers for redox-stable fuel electrodes in high-temperature CO₂ electrolysis and fuel-cell operation.