Comprehensive analysis of a full-scale solid oxide fuel cell stack fueled by ammonia

• Demonstrates effective ammonia use as fuel in full-scale solid oxide fuel cell stacks. • Compares pure, fully reformed, and partially pre-reformed ammonia performance. • Identifies long-term degradation patterns and optimal operating conditions. • Defines operating map linking current, utilization, and performance for NH 3 -SOFCs. Ammonia represents a promising alternative fuel and hydrogen carrier for power generation due to its advantages in storage and transportation compared to those of hydrogen. However, challenges persist in the direct use of ammonia in solid oxide fuel cells (SOFCs), particularly with respect to performance degradation—an issue that necessitates comprehensive investigation at the full-stack scale. This study examines a ten-cell full-size SOFC stack under various operating conditions to evaluate the viability of ammonia as a direct fuel. Experiments were conducted using pure ammonia, pure hydrogen, fully reformed ammonia, and 50 % pre-reformed ammonia at three operating temperatures (660°C, 710 °C, and 760 °C). Performance was characterized through current–voltage curves, electrochemical impedance spectroscopy, and continuous monitoring of residual ammonia in the exhaust using Fourier-transform infrared spectroscopy. A 200-hour durability test was performed to assess long-term stability. The results demonstrated that at temperatures of ≥ 710 °C, ammonia-fueled SOFCs performed comparably to hydrogen-fueled configurations within typical operating ranges (0.2–0.5 A/cm 2 ). The stack achieved optimal performance at 55–80 % fuel utilization. The ammonia-fueled configurations exhibited different voltage behaviors at higher fuel utilizations compared with those of the hydrogen-fueled configurations. The residual ammonia concentration in the anode off-gas remained well below the safety thresholds. Long-term testing demonstrated an initial degradation that eventually stabilized at a more sustainable rate. These findings validate ammonia as a viable fuel for SOFC stacks when operated at appropriate temperatures (≥710 °C) and optimal fuel utilization, offering a pathway toward sustainable, carbon-free ammonia energy systems.