Speakers

Carbon-free ammonia offers higher hydrogen content and volumetric energy density compared to pure hydrogen. Effective electrocatalytic materials are essential for NH₃ fuel decomposition into nitrogen (N₂) and hydrogen (H₂) at intermediate temperatures (500-700 °C) anode, particularly for use in oxygen ion-conducting solid oxide fuel cells (OSOFCs). The non-stoichiometric strontium perovskites such as Sr₂Fe₁.₅_±xMo₀.₅_±yO₆ (SFM) and Sr_1-xTi_1-yN_yO₃ ​(STN) exhibit mixed valence states at the B-site (Fe, Mo, Ti and dopant N), which promote the formation of oxygen vacancies. These vacancies enhance both ionic and electronic conductivity, thereby improving fuel gas adsorption and electrocatalytic activity. The hydrogen generated from ammonia decomposition is then electrochemically oxidized to produce electrical energy. In this study, SFM and STN anodes were synthesized with varying B-site stoichiometry to modulate the concentration of oxygen vacancies and to induce the segregation of Fe-, Mo- and N-based secondary phases. These anodes were co-fired with a ceria-based electrolyte (LSBC). The in-situ reduction of Fe-, Mo- and N-​containing nanoparticles on the ande grains further enhanced the ammonia cracking capability during symmetric SOFC operation. The power density of the fuel cells increased depending on the nature of the B-site  defects. These findings demonstrate that cost-effective, non-stoichiometric modulation of the B-site valence and composition in SFM and STN are promising and flexible strategy for improving power density in NH₃-fuelled OSOFCs.