Advanced design strategies for highly efficient and durable anodes in direct ammonia solid oxide fuel cells

Ammonia is increasingly considered a promising zero-carbon hydrogen energy carrier owing to its favorable properties for storage, transport, and distribution. The direct utilization of ammonia in solid oxide fuel cells (SOFCs) has the potential to offer a highly efficient power source with high energy density. However, the poor stability and low catalytic activity of conventional Ni-based anodes for ammonia utilization significantly limit the performance and application of ammonia SOFCs. Here, we report the development of a new anode composed of exsolved nanoparticles from an Sr(Ti, Fe, Ru)O_3−δ (STFR) perovskite structure and a catalytic iron layer (STFR + Fe), which considerably enhances activity and durability for ammonia utilization. The La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ electrolyte-supported cell with an STFR + Fe anode shows peak power densities of 1.25 W/cm² at 800 °C and 0.76 W/cm² at 700 °C with NH₃ as fuel. These power densities surpass 85% of those achieved using H₂ as fuel and are significantly higher than those of cells with an Ni–Ce_0.9Gd_0.1O_2−δ (Ni-GDC) anode (0.38 W/cm² at 700 °C). Additionally, the STFR-Fe anode demonstrates exceptional stability when operating at a constant voltage of 0.75 V at 800 °C. The current density of the cell exhibits a marginal decrease from 1.33 A/cm² to 1.32 A/cm² after 120 h of testing, corresponding to a degradation rate of 0.006%/h, which is substantially lower than that of the Ni-GDC cell (degradation rate 0.283%/h). This degradation rate is the lowest ever reported, highlighting the superior stability of the STFR + Fe anode system.