Enhanced coupling of the tubular direct ammonia solid oxide fuel cells for efficient ammonia-to-power

Direct ammonia solid oxide fuel cells (DA-SOFCs) have triggered great interest due to their efficient power generation from ammonia directly. However, the compatible match of ammonia decomposition and electrooxidation in the DA-SOFCs remains greatly challenging due to their endo/exothermic properties. Herein, multi-sizes tubular DA-SOFCs were systematically investigated for performance evaluation of power output and ammonia decomposition. Accordingly, a multi-scale electro-thermo model for tubular DA-SOFC was established to intensify the synergy between complex physical-chemical processes and geometry. With the combination of experimental work and simulations, the effects of operating conditions and geometry were comprehensively evaluated. Significantly, the rates of ammonia decomposition and electrooxidation could be effectively matched through the optimization of operating conditions. The geometric design further enables the temperature-zoning of the two processes, competently enhancing the thermal coupling between them. Conclusively, the correlation equations linking the operating conditions, geometry and electrical efficiency were proposed for the scaling-up of tubular DA-SOFCs unit. The tubular DA-SOFC achieves 3.5 W with 60% electrical efficiency, and performed a satisfactory stability for over 330 h. This study provides guidance for oriented design of tubular DA-SOFCs with high electrical efficiency.